This means for every $10 you want to win on a spread bet, you have to bet $11. If the odds were even (also represented as +100 in American sports betting), an $11 bet would have a payout of $11 (so a total return of $22).
Decimal odds explained\n\n For example, a $100 bet made at decimal odds of 3.00 would return $300 ($100 x 3.00): $200 in profit and the original $100 amount risked. A $100 bet made at decimal odds of 1.50 would return $150: $50 in profit and the original $100 amount risked.