Depreciation for a rental property with different amounts in differen years via TT

When I moved overseas in 2018 I began renting out my house. The depreciation was approxiately 3,984 per year based on a 27.5 SL method for 2019 and 2020. This tax year 2021, when working on the rental income/expense in TT, I plugged in the same figures (I used the same home and land value), and the depreciation was just over 3,097 or something close. Why is there about a 1k difference this year than in the two previous years I though is should be the same with SL? 

Thanks