Home office expense calculation

Good afternoon,

 

My tax return 2020 was audited. It was about an item on Schedule 1 (line 11): "Certain business expenses of reservists, performing artists, and fee-basis government officials. Attach Form 2106"

that I think comes from my home office expense, including the previous home office from my previous rented home as well as the new one, there was an overlap of time also. I check the tax return but didn't find the information about how the expense was calculated. Is there any idea where to find the information?

 

Thank you.