Selection's index over/under 2.5 goals

Hi
I know I am being stupid but , when viewing over/under 2.5 goals
on Betfair  the 2 is by the under 2.5 goals and the 1 by over 2.5 goals.
Using those as the numbers for selection’s index sees to work the opposite way round
backing under 2.5 goals selection's index is 1. Someone please explain
why I am not seeing this correctly. Thanks
Mike

Probably you've got confused with index and rank.
The index is by BetFair order.
The rank is by the current price.

Many thanks, I knew I was missing something obvious