Hi @Holly Elliott-White,
Thank you for posting in this community.
I created four single-select columns in my case and used this formula =[number1]*[number2]*[number3]*[number4]
to calculate the result of multiplying the four columns of single-select values. The result runs well.
Since we can't reproduce your situation, we need to narrow down the problem and try some things. So, please kindly provide more information below to let us work further.
1.Please delete your calculated column and recreate them. Then see if the problem persists.
2.Whether all SharePoint lists have the same problem? You could create a new SharePoint list to check.
3.Try to use a different browser or your browser's InPrivate mode to see if the same error occurs.
4.If the problem persists, please share with me how you set up your selection columns and calculation formulas. This will help me to reproduce your problem better.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.