Integer underflow #165

Describe the bug
Integer underflow

To Reproduce

1. Type a large number as expense and enter
2. Budget is over
3. Integer underflow

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots

Please complete the following information:

• Device: [e.g. Pixel5]
• OS: [e.g. Android13]
• Version [e.g. 1.0-beta4]

Additional context
Add any other context about the problem here.