Retrieve variable from dialogue box

Hello,
At the start of my experiment I wish to get modulable parameters to use afterwards.
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However, when I try to use nb_rep adterwards to fix the number of repetitions in my loop, it tells me this variable does not exist. I wish to use only the builder.

This is the error I get :
NameError: name ‘nb_rep’ is not defined
################ Experiment ended with exit code 1 [pid:17080] ################

Thank you so much for your help !