Reset sequence new sheet
When I create a new sheet in Excel, it's automatically named Sheet1, Sheet2, and so on. In my workbook, I'm using only three sheets, but when I create a new one, it's automatically named Sheet120. I ...
Forum Discussion
I think Excel keeps track (somewhere in the background) of how many sheets have been created in any given workbook. So even if you currently have only three, if you've used and discarded -- or whatever --others, that could be the cause.
That said, it's probably better practice to give more descriptive names to the tabs anyway. For example, I often have "Basic Data" as one tab--sometimes I'll call it "Data Table" or plural "Data Tables"--and another might be "Current Summary" and another could be "Background calcs"
When you do that, especially if some of the formulas refer to other sheets, the formulas will be more intelligible. "Sheet 1" and "Sheet 2" etc makes for ambiguities.