it's 10 park days + 10 visits to the water parks, dq, oak trail golf, wwos. the water park fun & more are a separate form of admission than MYW base tickets and aren't subject to the park hopping rules. so you can visit MK and DQ on the same day without park hopping for example. and visiting multiple plus parks in a day consume take away the multiple visits. so to do DQ and TL in one day is 2 visits that day, leaving 8 (for example).
because the ticket expires 14 days after first use, you can't get 20 days out of it unless you add the no expiration option.