Something fishy with marketstat sell/volume

[Zed Ahri]

Taking an example item:

http://api.eve-central.com/api/marketstat?typeid=31061&usesystem=30000142&hours=24

<sell><volume>52</volume>

Changing the parameter hours has no effect unless I put it to very small in which case volume is 0.

Looking from in game market, today 10 have sold, yesterday 6.

There are ~33 items in sell orders atm.

What on earth is that 52 supposed to describe?

Ps. quicklookg for the same item in same system is able to nicely see that there are 33 in sell orders.