what's important is to determine why there is a difference. if you were to sell the property the depreciation recapture would be based on the larger of depreciation allowed (taken) or allowable (the amount that should have been taken based on the applicable rate in effect in the year the property was placed into service). you can override the calculated amount but this will prevent e-filing.
here's a link to IRS PUB 946 which details depreciation lives and methods.
https://www.irs.gov/pub/irs-pdf/p946.pdf
