How it works
Book A prices the home side at 2.10, book B prices «home not to win» at 2.10: 1/2.10 + 1/2.10 = 95.2% — the missing 4.8% is your locked margin if stakes are sized proportionally.
Why it is harder than it looks
Bookmakers hunt arbers actively: accounts get limited or closed within weeks; lines move while you place the second leg, leaving one side uncovered; palpable-error rules let books void one leg after the fact. Sustainable arbing is a logistics business of many accounts, not a casual strategy.
Not what ScanGoal does
In Russian, «scanner» usually means an arb scanner. ScanGoal is a different tool: it scans match state — pressure, tempo, goal probability — not price differences between books.