How do I enter a non-cash donation of $600 in It's Deductible? I keep getting an error message that says value must be below 500.

[mesquitebean]

I assume you mean a single item with that value.   The total of multiple items in a donation can exceed that amount, but not a single item.

In ItsDeductible you can't enter a single item that's more than $500 in value since additional questions are required to report it on Form 8283 that are only present in the TurboTax program.

You can enter that item into the TurboTax program when you prepare your tax return, and it will ask you for the additional information.

If you want to see what additional info you will need for the item when you prepare the return, here's a Form 8283:
https://www.irs.gov/pub/irs-pdf/f8283.pdf

Look at the 6 columns d-i in Part I.