Seen from both sides, "What does a hedge bet mean?" leads to one event. Hedging and arbitrage both mean betting on more than one side of the same event. A hedge does it after a first bet is already placed, to lock in part of a win or cut a loss. Arbitrage does it at the start, across different books whose prices disagree, so that every outcome returns a little more than the total stake. What they share is the arithmetic of splitting stakes between opposite results.
What does a hedge bet mean in practice? A bettor holds a ticket that now looks likely to win, or likely to lose, and places a second bet on the opposite result. How does hedge betting work in numbers? A parlay needing one last leg at long odds can be hedged by backing the other side of that leg, so the bettor collects something whichever way it goes, at the cost of part of the upside first hoped for.
How much to hedge a bet depends on the aim. To guarantee the same return on both sides, divide the first ticket's potential return by the decimal odds of the opposite side, and stake that. To only cover the first stake, bet less. Should I hedge my bet is a question about risk: every hedge pays the book's margin a second time, so a hedge bet strategy used on every ticket slowly costs real money.
Two books can settle the same event differently, for example on retirements or overtime, which can leave one side of an arbitrage unpaid.
Add up one divided by each best price across all outcomes; when the total falls below one, the prices leave room for a guaranteed return.
Gaps are usually one or two percent and last minutes, so the return has to be weighed against the hours spent searching for them.
The budget is divided in proportion to the inverse of each best price, so every possible outcome returns about the same total.