formatting – Excel rounds numbers, not the displayed ones but in the formula-part. I dont wnat that

Sorry for the dumb question.

So in my dataset I put, for example, the number 1.30 down for a patient.
It is displayed as 1.30 (the cell is formatted as a number, decimals to 2). However, when I click on the cell, in the upper part where you also type formula’s, the number is 1.3.

When I change it there to 1.30, it automatically turns back to 1.3. When I work with this number in formula’s etc. the returned number has 1 decimal…. Why does this happen?