If any items can be identified specifically to NY or TN, you will want to allocate to that state,  If anything is an annual total, you can prorate using a percentage (11/12) to New York.  For example, if it is interest income you received while in New York, it would be 100% to New York.  If you received a monthly amount, 11/12 would be NY and 1/12 would be allocated to TN.

Thank you so much! So I would prorate even if it's just my income from my NY-based employer? and what do you I put in the description box?

If you worked at an established office in TN even though paid by a NY based company then the income is not NY sourced and you would prorate.  92% would be the NY percentage (11/12).  

However if you worked from home in TN because of employer necessity (Covid-related, for example) then the income is still NY sourced and you do not need to prorate.  

You may need to clarify a bit on the description box question.  I don't see that when I allocate in the NY state return.  

TN does not tax wages so you don't need to file for that income in TN if you prorate.