Total rounds in fight markets can depend on if the fight is a championship fight with 12 rounds, as some fights can be scheduled for 4, 6, 8 or 10 rounds depending on the experience and level of the match-up.
Total rounds will be an overs/unders style market, using the Saul Alvarez v Jermell Charlo example. The market can be displayed as Over (+10.5) Or Under (+10.5).
For Total Rounds settlement purposes where half a round is stated then 1 minute 30 seconds of the respective round will define the 'half' to determine under or over.
If the number of rounds for a fight is changed after this market has been set then all bets will be void.