How to handle old user input in a newly disabled field

I have a form where there is a input thats only enabled with certain other settings. However there is a case where a user enters something in that conitional field, and then changes the other setting such that the conitional field is now disabled.

From this:

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To this:

mockup

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Whats the proper way to handle this situation? Leave the user input displayed (and ignore it)? Clear it out every time you toggle the conditional field?