I have my doubts that as a betfair customer since 2004 you are genuinely unaware of how the traded amount is calculated but....
The amount displayed as traded at any given price on Betfair is equivalent to twice the amount that has been backed at that price i.e.
If you place £2 on selection A at 1.01 that will equate to £4 being traded at 1.01.
If you place £2 on selection X at 1000 that will equate to £4 being traded at 1000.
If it displays £30 traded at a price of 110 on selection Y, that means that a total of £15 has been backed on selection Y at that price of 110, as at that time.
On the b*td*q exchange, the amount displayed as traded at any given price is calculated as the amount staked at that price multiplied by the price (much as you described above) i.e.
If you place £100 on selection A at 1.01 that will equate to £101 being traded at 1.01.
If you place £6 on selection X at 1000 that will equate to £6000 being traded at 1000.
You should have posted that twice fergus.
The other site does it that way to inflate overall volume.
I ask £2 at 100/1
You take £2 at 100/1
it will appear as £4 in volume.
so if you place a bet of £2 and you see that:
£2000 has been matched at those odds
£352 is waiting to be matched including your bet.
It means that
+ £350 times 2
= £2700 has to appear in the VOLUME MATCHED before your bet is the front of the cue*
*bear in mind, if people cancel their bets, yours moves up sooner.