So first I'll clarify what IVs are, so these is no confusion when I answer this: each stat in your Pokemon has an IV value, ranging from 0 to 31. These are completely randomised and you have no control over them. Each IV point adds one stat point, at least at level 100 - at lower levels, IVs are worth less due to how they are distributed as you level up (this prevents super overpowered level 1s with 31 points in each stat due to perfect IVs). In competitive battling, having perfect IVs in each stat is nearly mandatory, as every additional point can mean the difference between life and death.
The first thing I'll say is that IV calculators are not correct, especially if the EVs you add into it aren't 100% accurate. If you can give them all the correct detials with 100% accuracy, your chance of having an accurate result is better. The calculator may be correct with Flareon's IVs, or it may be completely wrong. All depends on what you added in.
A Pokemon's characteristic serves as an indicator of which stat has your Pokemon's best IV, and can also give you a rough idea of what the specific value is. If the highest IV is a tie, then the characteristic shown will be determined by the Pokemon's personality values, another extremely technical hidden mechanic that I won't talk about to avoid confusing you. "Capable of taking hits" means that Flareon's Defence stat is or is tied as one of its best IVs. It also indicates that its Defence IV is one of the following numbers: 1, 6, 11, 16, 21, 26, 31. This means that it is possible that Flareon has a perfect 31 Defence IV. It doesn't tell you if there are stats that tied with Defence for the best IV, and it does not tell you which of those numbers the IV is; again, it is a vague indicator of its stats. Because of Flareon's characteristic, it is impossible for its Defence IV to be 30, which is an error on the calculator's part as it states that its Defence may be 30 or 31.
So it seems like you're in the dark with the rest of Flareon's stats, huh? Luckily these is another system to find out some more info on its IVs, called the IV Judge, a trainer who you can find in the Kiloude City Pokemon Centre in X/Y or the Battle Resort Pokemon Centre in OR/AS. Everything he says gives you some insight on your Pokemon's IVs. Here's a huge copy-paste from Bulbapedia that will explain what everything he says may mean:
>##Highest individual stat
"Incidentally, I would say its greatest potential lies in its (best stat here)."
(If the Pokémon has two or more equally good best stats, then he will add one of the following lines:)
"But its Attack stat is good, too."
"Hmm. And its Defense stat is good, too."
"Although its Sp. Atk stat is equally good."
"Its Sp. Def stat seems just as good, though."
"And, well, its Speed stat is good, too."
>To describe the value of the Pokémon's highest IV(s), he will use one of the following lines:
IV range of 0-15: "It has rather decent stats, I'd say. That's how I judge it."
IV range of 16-25: "It's definitely got some good stats. That's how I judge it."
IV range 26-30: "This Pokémon has some fantastic stats. That's how I judge it."
IV of 31: "Stats like those... They simply can't be beat! That's how I judge it."
>##Lowest individual stat
If a Pokémon has any IV of 0, he will use one of the following lines:
"But its HP... It's pretty dismal, you know?"
"But that Attack stat... It's terrible..."
"But how can you make it through battle with this kind of Defense stat?"
"But this Sp. Atk won't even leave a scratch on an opponent..."
"But this low of a Sp. Def stat is going to leave you high and dry..."
"But you won't get anywhere fast with this low of a Speed stat..."
>(And if there are 2 or more IVs of 0, then he will also use one of the following lines:)
"And that's quite a disappointing Attack stat there, isn't it?"
"And that Defense stat is nothing to write home about, you know?"
"And I'm afraid that its Sp. Atk is pretty bad, too..."
"And it looks like it's no great shakes when it comes to Sp. Def either..."
"And that Speed stat... Well, it's nothing to brag about, that's for sure."
In the rare event that all six of the Pokémon's IVs are 0, then he will describe how all its stats are its best stats, and then describe how all of them are bad.
So basically, if he tells you its greatest potential lies in its Defence and then says that its stats cannot be beat, then your Flareon has perfect Defence IVs! Even better, if he states that its greatest potential lies in multiple stats and then says that its stats cannot be beat, that means that every stat he mentioned has perfect IVs. If he mentions that your Pokemon has some fantastic stats, or mentions anything other than "those stats cannot be beaten!", then your Flareon has no perfect IVs and the calculator was wrong.
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