thanks everyone for replay.
I looked at .... (
http://www.realoem.com/bmw/enUS/show...diagId=61_2815)
and yes they mentioned "Note:
The installed 90Ah AGM battery is to be
replaced by the 92Ah AGM battery!"
BMW seems they always use the battery AH number.
I've been looking online for battery replacement and reading more about batteries. People always look for CCA and its the most important when you buy a new battery and it always should match your current battery or higher.
now the battery I posted before is 110AH, will that affect the car or something ????