I have a very simple sheet that is used to log activity for an after-action report. The form that employees fill out has a simple, number-validated field to enter start time. They are asked to enter time in 24-hour format with digits only (ie. 2315 or 0800). The sheet is automatically appending a "d" to the end of the number (making it 2315d or 0800d). If I add a new row or change an existing row and use traditional time format (08:00) or any combination of characters that includes more than just numbers, it doesn't happen. It also only happens in the start time column. The end time column doesn't do that.
I'm sure I can fix the issue by creating a new column and deleting the original. I'll do that for now, but to avoid a similar issue in the future, does anyone know why this happens?