Form 1098 and confusing message "Beginning principal must be entered"

I received this 1098 form from my bank for the Home Equity Line Of Credit:

1098_Heloc.png

 

End entered the data in the TurboTax form when it was asking about it:

Entered1098Data.png

 

Towards the end Turbotax asked me to make this correction

The validation errorThe validation error

 

Where do I get the value for the "Beginning balance"  taking into account it doesn't exist in 1098?