I am confused and have been searching for hours, my internship boss created a report form on Microsoft where he has added the text below

Original Bill Amount:
Total Disputes:
Total DNT’s:
Adjusted Amount:
Sam Simon presents…Payment:
Personal Payment:
Balance:
he inputs his payments right next to the text above and by hand figures out what the balance is. We are trying to figure out how to get the adjusted amount and personal payment to automatically add and subtract the numbers.
the only field that pops up when i double click is Text form field options