The offices ordered a total of 3 offices * 10 sandwiches each = <<3*10=30>>30 sandwiches.
So the group of customers must have ordered 54 total sandwiches – 30 sandwiches for the offices = <<54-30=24>>24 sandwiches.
This is a total of 24 sandwiches / 4 sandwiches per customer = <<24/4=6>>6 customers who ordered a sandwich.
As only half the group ordered a bacon sandwich, the entire group must have consisted of 6 customers * 2 = <<6*2=12>>12 customers.
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