I've got a couple different PowerApps all having the same problem. When a form submits a number to a Google Sheet, be it a date, time, static number, dynamic number generated by a formula, an apostrophe appears infront of the number in the Google Sheet. The apostrophe doesn't appear if there are letters mixed in with the numbers, with the exception of date/times with AM/PM. The apostrophe doesn't show in the sheet unless you click the cell and look at its full value in the formula bar.
I'm not sure if this is a problem with Sheets or PowerApps.
I've noticed this problem too, and it has kept me from using Sheets in any application where data needs to be submitted or patched. It seems like any numerical or date value submitted to Sheets gets an apostrophe added. The single apostrophe formats the cell as plain text, and it's an issue I've had with Google Forms submissions as well. I don't know if it's a PowerApps issue or Sheets issue though.
There's a workaround here using another column with a formula to remove the apostrophe, but I don't know how useful it will be for your application.