correct rental property depreciation

Do you have some justifiable reason for adjusting your original Cost Basis just a bit?  It sounds like you initially were pretty close, if the difference in depreciation each year is only $100.  Over the entire 27.5 years of depreciation, this amounts to about $2700. 

You can Amend your last three years returns to correct a depreciation error, if:

• You claimed the incorrect amount because of a mathematical error made in any year.
• You claimed the incorrect amount because of a posting error made in any year.
• You claimed the incorrect amount on property placed in service by you in tax years ending before the statute of limitations has expired.

Here's more discussion on Incorrect Depreciation you may find helpful.
 

1. Go into the "asset" for depreciation.
2. Change the amount to the correct number.
3. Look for the place where it asks for the "prior depreciation" and change it to the GREATER of (a) the actual depreciation taken or (b) the amount of depreciation that SHOULD have been taken if it was done correctly.
4. You have the option to amend prior years to correct them.