A unit is your lowest denominator.
If your smallest bet is $10 - that is one unit for you. You will usually place bets in multiples of units.
So one unit on the Browns and 3 units on the fins - translation = $10 on the Browns and $30 on the fins.
The amount of one unit is different for every bettor. For people that bet a lot, the unit is also their standard bet and they only bet more than one unit on bets that really stand out to them. This is a way of keeping yourself both organized and to make sure that you don't go and blow your budget on a single game.
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