each column or row cell now only has 1 digit
The column to the left of your digit has text that is wrapping to a second line within that cell. All it takes is one cell in the row to do this and the entire row will do it. All cells in a row are the same height (unless you have merged cells which you are not showing in your screenshot). Your screenshot does not show the text or your digit "taking up the cell and the one below". Each is in one cell as it should be. The cell/row height increased is all.
Was this file imported from another app, like Excel? It is possible it did not set the row heights upon import and left them to vary with the contents of the cells. It is possible the rows heights "fix" themselves to fit the data when you edit. If you want them to be a particular height and not change, select the rows you are concerned about, go to the Table tab in the sidebar on the right, scroll down until you see "row height", and type a number in there (even the same number will do if it is what you want).
Conversely, if it was imported it is possible it did set the row heights but didn't actually apply those settings to what you see and whenever you edit a row it "fixes" them. Just throwing out ideas. I've not seen this happen