The numbers in the table are unreadable from the stringing decimal places.
In the table cell for Trinity Paid For Trinity, the number was not rounded to the nearest hundredths place and continues on to the next cell, affecting the readability of the number for Trinity paid For Neo. After checking, I found out that all of the numbers run on like this if the amount was converted to something other than USD and this affects the readability of the entire table.
Recommendation: Round the decimal to the nearest hundredths place for conversions.
Both table formats takes time and effort to figure out the information.
The table cell chart at the top could improve on efficiency because the user needs to look at the row and then the column to figure out the number, and then check to see if the two headers were correct. It also seems like this information isn't that important since the main function of the app is to calculate who owes who how much money. The table at the bottom could improve because the Payer and Payee is arranged vertically if there are multiple, but the amounts are horizontal. This makes it more difficult for the user to match up the amounts to the Payer and Payee.
Recommendation: For the spreadsheet table at the bottom with all the information, make the amounts vertical and line up with the Payer and Payee. For the table cell chart at the top, either simplify the information into lines, make the table collapsable, or remove the table entirely.
The inputs allow you to enter a negative ammount.
Entering a negative amount is problematic because it affects who owes who how much. Was the negative number a mistake or did the other person actually owe them? It makes who the payer and payee is unclear. Most likely, it was unintentional, and the user should be prevented from making this error.
Recommendation: Prevent the user from entering a negative value by setting the min number to 0 for inputs. Doing this will also let the user know that they can't enter a negative number if they try to type it in (which goes into Error reporting, diagnosis, and recovery).
There is no log out button.
There is no log out button on the page, so I didn't realize that I was even logged in. This has severe safety issues because if the user logs onto someone else's computer, other people can view and edit their expenses. It is difficult to figure out how to log out, and if you can't figure it out, then others can view your personal information. This also goes into efficiency issues because to log out, the user needs to go to clear browsing data, click less than one hour ago, and then clear cookies. There is, however, a log in button, but it disappears after the user logs in. This violates Consistency and Standards for the Nielsen Heuristics because if there is a log in button, there should also be a log out button.
Recommendation: Include a log out button.