I can't reproduce your results
I put the 2 numbers you specify in a spreadsheet then opened the data in Tableau as a number and as a string as well. Tableau is showing the number perfectly:
The only thing I can think that might be interfering is Google Sheets, but your Tableau screenshot looks fine.
Tableau tries to determine the data type as it is loaded
if the type is incorrect go to the data tab and change the type there
you should be a string
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Thanks for the help, I'm looking at google sheet now, but it has worked in the past so I'm stumped