How do I lock down a field in a Field Calculation?

It appears that users can manipulate the cost that appears in a Field Calculation field. We want the user to see the team cost, but they should not be able to change it.

I can change the field myself in Preview Mode.

How do I lock down the field so it can't be edited? I do not see a Read Only option.

 I found the answer buried in the Options settings.

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