Have you tried adding a condition on the update date of the user
If this reply answered your question, please Accept As Solution to help other who may have a same problem. Give Kudos 😉
I would suggest below, when brand domain is updated at that same time update another CP with current date value + 4 days (since after 4 days you want to trigger email notification).
Write one sav to sav which compares current time with value of cp that you are updating in above step.
Once it matches update that same CP with Generate_Email_Date
Write one user update rule which check for update on that CP value
CP value updated and CP Like 'Generate_Email%' with action Notify as Email.
Currently, Generate Email does not have Execute on feature; hence, OOTB can't be achieved to delay email creation after 4 days
Using inline processor, whenever new value of subbrand is updated, use another custom property, and using detective user update rule generate email id after 4 days as workaround