Strange output from "select_multiple" questions

Support
10

I'm not sure if there it's a reliable way but in my case, it worked:

  1. Select a cell with the wrong value, eg. A4 43686
  2. Click Format->Number->Date
  3. It will give you 09/08/2019 what might indicate selected values were 9, 8, 19

but you have only 12 options in the form you attached...
did you have more by any chance? or maybe you used another form?