is box 10 what was taken out of my check every 2 weeks and put into my flex spending account that my employer does not repay me for ? should i fill it if not reinbursed?

Yes, you put in pre-tax dollars. You must show that you used this money as intended or it becomes taxable income. Once you fill in your childcare expenses, the program will understand and match things up. If you spent less, the excess will be taxable.