How to understanding shopping cart exit rate in goal visualization

How to understanding shopping cart exit rate in goal visualization

We have a goal funnel set up with
(simplified)
Shopping Cart (not required)
Checkout
Checkout Completed
(It's possible that someone adds an item to their cart, goes back and
finds another product to add to their cart.)
Right now the Cart exit rate is being reported at, say, 60%. Does this
mean that 60% of customers bailed on the Cart and never came back (because
if they had gone through, Google would 'backfill' this 'exit' out of the
process) or could it mean that some of those 60% left, added another
product and then continued forward (meaning Google reports the 1st cart
visit as an exit, and the second as a completion)