I know these handicaps can be complicated at first.

Arsenal -1.25

• Bet wins if Arsenal wins by a goal margin of 2 or more goals (for example 2-0 3-1 ...)
• In case they win by exactly a 1 goal margen (for example 1-0 2-1 ...) half of te stake is returned so it is half a loss.
• All Arsenal draws an losses fully lose the bet.

So If Arsenal only wins their match by a 1 goal margin and your other 4 bets fully cover their handicap your record will be 4W-0.5L which is better then 4W-1L

These lines are set so money that comes in on the betting market is close to 50-50 split on each side.
I hope this makes it more clear.