Home Office deduction partial year not possible?

Looking to put in for a partial year deduction for home office: only used home office for 3 months. 

TT asks for  that info to be entered as follows:

"In 2024, how many months did __ use this office?"

So, I enter 3 months.  

But the final output only shows the home office deduction for a full year, not the partial year. 

Anyone with experience in this, please advise!

Thank you very much!