Am I missing someting?

I bet with Xbet spreads and fixed.  I fancy Glamorgan to beat sorry and was looking to wager £300.  Their Fixed Odds price is 1.73

So a profit of £219 if they win.....

But in their 25 index you can buy Glamorgan at 13.  So if they win you win 12 times your stake and if they lose 12 times ur stake.

So if I buy at 13 for £23.  If they win I win 12 x £23 = £276 and if they lose 13 x £23 = £299

So I bet a pound less but win £57 more ???

I must be missing something ??