OK, that looks like a form, not a collection. Also, you weren’t showing the total balance field in your first screenshot and mentioned that you wanted to calculate the final balance…not the total balance. So, I was a little confused by your question.
First of all, can you confirm that the screen you are showing is a Form or an Edit screen? Are you adding a new row or editing an existing row? Does it have Submit/Cancel buttons at the bottom? If it is a form, you can’t perform calculations in real time because the calculations only occur once the row is added to the table. That only happens when you click on Submit. Also, you will not be able to show a computed value in an entry component, because the entry component is meant for user entry…not for displaying computed values…so you would need a regular text component.
If you want to calculate values in a form in real time, you will need to use a custom form, but it will cost you additional updates.
Screenshots that show the entire screen are a lot more useful that cropped images because there is a lot of sub context that I can obtain from other parts of your screenshot that you may not realize are important.