The Leppa Berry's stats are 10 for all but Dry.
The Sitrus Berry's stats are 10 for all but Spicy.
The Chesto Berry's stat is only 10 for Dry.
So, the total stats for the Poffin would be 20 for Dry, 10 for Spicy, 20 for Sweet, 20 for Bitter, and 20 for Sour.
According to a video from Austin John Plays, at timestamp 8:06 he says "Never cook two of the same Poffin". In this case, 2 of the same berries.
To prevent this issue, I'd suggest adding 4 different berries to make your Poffins.