If you get an extra turn (4 match) the turn counter does not go up but does not go down either. If you get an extra turn (match 5) the turn counter goes up by one. The extra turns do not stack on each other after the net gain of one. This is implemented by design to limit the number of moves a person can make and to shorten the time it takes to play a map. If left unchecked players would hit the no more moves cap and also complain about how long it takes to play a map and how the amount of time invested does not pay as much as they were expecting. This is why they decreased the move count from 15 to 8 and increased the payout.