`beforeSubmit` for modifying the record being save...
# suitescript
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beforeSubmit
for modifying the record being saved;
afterSubmit
for affecting changes to other records based on teh submit (email notifications, send data to external systems, etc):

https://www.youtube.com/watch?v=-fh7UiSuzMQ&list=PLG2tK6Va2WUCseA3viGC2oYPkyA45wfA-