How does Block Field Updates work?
Hello,
I'm trying to block field updates to the Original Source field, as you can see below:

The idea is to let this field get populated once and then never get populated again. Ideally a sales rep will select a value for this in SFDC and it will sync to Marketo and get locked in.
I looked at the options to block updates and find them confusing. I don't know which one to select.

Should I just select all of them if I don't want this field to get updated down the road? If I block Salesforce Sync, will that mean I won't be able to update it the first and only time I want it updated? If the field is empty and I block it, will Marketo update it the first time and then stop updating after that?
Thank you in advance.