CVS Coke Products $5 ECBs deal may have more than 1 limit!

I went with my ecbs in hand to purchase the Coke deal earlier today.  Coke products are 5 for $15, then get $5 in Extra Care Bucks back with one limit per Extra Care Card member.  I purchased 5 Coke products and got the $5 ecbs on my receipt.  Then I made a second purchase of 5 Coke products plus a filler item since I had $19 in ecbs.  When I got the second receipt, I got another $5 ecbs!!!  I am not sure what the limit is, so I may go back and get 5 more Coke products.  I would be interested to know what the limit is.  Sometimes there are 4!