Welcome to Ironworks !
I am not sure what your question is, but only warrior character classes can get percentiles of strenghth 18 like the 18/00 you mentioned.
Or is your question even more basic ?
The games of the BG series are a rather exact application of AD&D 2nd edition rules for paper and pen roleplaying games to CRPGs. In the beginning the game guides you through a process of generating your personal character. The "talents" are measured in character stats in 6 areas and can range from 3-18 with 18 being the best. In PnP games theses stats are rolled with 3 6-sided standard dies (3d6). The game engine emulates that in the chracter generation process and that is why you have seen people discussing "rolling characters" here. The game allows you to redistribute the total points "rolled" for your new character between the 6 different areas of abilities.
I hope that helps at least a bit.
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So long !
R³ - proud to be the official spokesman for the most noble Lady Bilqis, Desert Rose of Ironworks
Btw, the cow is queuing in the slaughterhouse right now !