+5 -6 = -1. They lost 1 yard
They got 5 yards so 0+5=5 but then they lost 6 yards so 5-6= -1 as the numbers are negative, that means that they lost one yard
The team gained 5 yards and then lost 6 yards, resulting in a total change of -1 yard. This means the team is behind by 1 yard compared to their starting position.
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