This might be tricky to explain if you're inexperienced with EVs. I'll do my best to dumb it down, but if you have any questions, leave a comment. I'll tackle the main question last.
Don't you need 4 EVs to get a stat increase?
Sort of. This only fully applies at level 100.
While the stat formula does divide your Pokemon's EV value by 4 (which would make sense with this statement), it also multiplies it by your Pokemon's level, then divides it by 100. So, essentially, as I explained in this incredibly long answer, the percentage of your Pokemon's EVs that contribute to its stat is equal to its level. This means that the common belief that 4 EVs = 1 stat point only applies at level 100, where EVs are multiplied by 100. At any other level the percentage will be lower, essentially causing the amount of EVs you need for a stat increase to go up.
So, based on that, you can just follow the forumla [Pokemon's EVs]/4 x ([Pokemon's level]/100) to know how many stat points your Pokemon's EVs add. If you want to know how many EVs it takes for your Pokemon's stat to increase, take that formula and put your Pokemon's EVs at 0. Keep increasing the number by 1 until the answer you get is larger than 1. Whatever number of EVs you had is the amount you need for a stat increase. (In an example for a level 50 Pokemon, it took 8 EVs for the answer to reach 1, therefore it should get 1 stat point increase every 8 EVs it gets.)
I'm too tired to figure out if there's an easier way to do that. :P
In the first level of super training it says +4 base stat increase. So does that mean I have 16 EVs from 1 super training?
No, what makes you think that? It says +4, so you will have 4 more EVs from that Super Training game. Very simple.
Also do you get EVs in double battles?
Yes you do, pretty much the same way you get EVs in singles. Every Pokemon has an "EV yield". When a Pokemon faints, all the Pokemon that fought it (or have the Exp Share) will gain its EV yield, which will be added to its total EVs. For example, if I took down a Pidgey, whose EV yield is 1 Speed, all my Pokemon that fought that Pidgey would get 1 Speed EV.
The same happens in double battles, except it's likely that more of your Pokemon will get EVs since you have 2 in battle at once, each receiving EVs from every Pokemon that faints.
How to calculate EVs in Super Training?
First, find how many EVs your Pokemon has. In Super Training, there's a graph that shows your Pokemon's "base stats" (as the game calls them) which are really just its EVs. Based on the graph, you can get a rough estimate of what your Pokemon's EVs in each stat are. Remember, the maximum number of EVs your Pokemon can have in one stat is 252, so base your estimate off of that.
If you want a specific value, get yourself a Reset Bag and save the game. Then, use the Reset Bag on your Pokemon. The game will briefly show how many EVs it lost (which should be all of them). Take a look and make a note of them. Then, turn the game off without saving so you don't lose any EVs.
Once you have a good enough idea of your Pokemon's EVs, take the formula from above and see what you get. [Pokemon's EVs]/4 x ([Pokemon's level]/100)
Whatever you got as an answer is the amount of stat points you Pokemon got from its EVs. If this isn't the type of "calculating" you were looking for, leave a comment. The question was a bit vague.
Credit to Bulbapedia for the stat formulas.
