Sage Fixed Assets

Hello, I added many old assets to SAGE but I'm still struggling with the older assets that are on their second half of life . For example, my building that was put into service in in 1991 is only 32 years through its 50 years but when I put in 18 years…

Is there somewhere that I can find details on the formulas used by sage to calculate deprecation? We are moving from Lawson Fixed Assets to Sage Fixed Assets and our calculations are not coming out correctly. Thanks