Add up numbers in PDF

Hi.

I'm working on a pdf file created in inDesign. It is a document (pdf) with which we let people make declarations. Thay can put the description and amount in the document en it will count al the bills as one total.

I thought ok that's easy with Acronbat Pro DC en the calculate field etc... but I'm keeping the error 109 with saving. And then It won't save.In the preview file it works.....

The 0,00 won't work... it's says >> This default value does not match the format (Number) specified. Please enter a  default value that matches the format or change the format in the Format panel to match this default value.

I need to count up 31 fields