How to calculate the time difference?

I followed these instructions to update my form https://form.jotformeu.com/83071712731350 unfortunately the results are not what I expected!

The Form Calculation Widget I created was intended to sum the VLK (Volunteer Lock Keeper) hours a volunteer the spent in the month. However adding a single hour to the matrix the Calculation results in 1e+55!

What have I done wrong?

Thanks for an excellent product. Really enjoy working with Jotform.

Best regards,

Howard (Canal River Trust Volunteer, Kenilworth, England)

We apologize for the inconvenience. For the time it is a little more complicated. TIme is calculated based on different intervals i.e. minutes, hours, days, weeks etc. The time has to be converted to Unix Epoch Time, calculated and then converted back to normal days/hours/minutes.

Here is a useful guide on this: https://www.jotform.com/help/443-Mastering-Date-and-Time-Calculation

Thanks Donald,

Thanks to your excellent product, there always is another answer.

I've now simplified the form using "sliders" to allow responders to select their hours.

Here is the new form https://form.jotformeu.com/83074922428359

Thanks for the excellent support.

Much appreciated.

Howard