If I have a number in a cell in an Excel sheet and format to use commas, then copy and paste it into a cell in on the demo site, it appears as it did in Excel. But, if I try to perform math on that cell, I get a #VALUE

example:
in Excel, enter the value 462345
Then format as a number to use commas
copy the cell
paste in cell L15 in the demo sheet
in cell L16 type =1+L15
the answer will be #VALUE

If we copy/paste values without commas, we do not see this behavior