How are the team ratings for each part of the squad (ATT/MID/Def) being calculat

So I don't know how I came across this but I'm really glad I did! oh and just wanted to say sorry for the length and t.i.a to anyone who reads this and/or offers any feedback/suggestions it is much appreciated!! 

Well the other day I got a few new players in ut and decided to make a whole new Squad.  so when in my squad (ultimate team>clubs>enter squad) everyone in the squad had a min. of a 92, 93, or 94 OVR rating and it gave me a rating of 92  (chem. 32/33) . then thinking alls well, head over to squad battles.  after selecting difficulty, &advancing with the same Squad I was talking about, it then now gives me an att./mid./def. of 86/85/78 !! ...so with everyone 92 or higher ovr and all in their preferred positions hows does that work??  so frustrated I did the math and also referred to how ea says they calculate ovr and everytime i added it up every way it came back as 92 except 90 when I added my bench players. anddd what's even more frustrating is that my previous squad i had before I made this one was 91 OVR and all my players were either 90, 91 or 92 min.  ovr (chem. 32/33) and also projected me as 91 OVR but when I would head into Squad battles it would tell me that my att./mid./def./ was 88/86/88 which I figured was a bug and didn't think much of it cus it wasnt that far off from 91...until i made this squad and a similar thing happened!!

so what the heck is going on and how does one determine att./mid./def. and/or ovr rating?? ea?? anyone?? comments, feedback, suggestions anything!! would be greatly appreciated, thanks!