Its an average of bids/asks at given amount of BTC.
My question is: why there is sometimes shown depth of up to 200 BTC, sometimes up to 500 BTC? What about to zoom there using mouse wheel, please, please?
Here is the fixed number pairs, I select them base on the volume.
mtgoxbtcusd 500
bitstampbtcusd 500
btcchinabtccny 200
btcebtcusd 200
btceltcusd 5000
btceltcbtc 5000
okcoinltccny 5000
All other pairs is dynamic.
I'd considered allow user custom the upper limit and still is in design. I think zoom won't be supported, it would be dropdown list instead of it.