Why is ES vol. on IB different than esignal

["etrader" <etrader@xxxxxxxxxx>]

Anyone know the reason why sometimes there is a
large discrepancy in volume bars on the ES
comparing a 1min vol. bars from IB data feed using
Hyperserver vs. esignal?  I have 1min. charts up
on 2 PC's which have their time synchronized but
there is a large discrepancy in the volume.  Any
ideas?

Thanks