Sometimes bookmakers make a lot of interesting errors which lead to very large and unrealistic surebets. It can happen due wrong displayed odds. For example:
It can happen due to a wrongly displayed handicap. On the first picture you can see a normal and real 1 x 2 odds. On the second one you can check the odds and handicaps.
The error here is in the handicap given in the match. The correct HC is +1 Goal for Treviso and for Ascoli, but in this case the handicap is messed up and the advantage is given to both home teams, which is obviously wrong. As we said before, avoid making surebets with such odds, just can try to bet if you wish, but your stake will be returned if the bookie notices the error before the match.