I live in IN. My job is based in IL. I work 3 days in IL and 2 days from home in IN. Do I only report income made while in IL as part of my nonresident IL tax return?

I am working on my IL nonresident return and it is asking about whether the income was earned in IL. However, my employer will not provide a letter with company letterhead that shows either the number of days I was in the office in 2024, or the amount of money I made while working from IL.