What should I put if my 1098 form for a HELOC is blank in box 2? Should I use the balance as of Jan 1 2024?

We got a 1098 for our HELOC and we paid a total of 1806.67 in interest on it in 2024, however the outstanding balance box 2 is blank on the form. Do I use the balance as of Jan 1 2024? December 31st 2024? It is a HELOC so the balance goes up and down all the time.