Gradual doesn't mean you have to use the value from the last callback though (since if we aren't in this case we use P-control to assign m_dSyncAdjustment and that is a gradual change only if the change in error is gradual (which it most likely is)). 

I guess my question is -- is the only reason this uses the previous value because we don't know what to do in this case or is there a reason behind using the previous callback's m_dSyncAdjustment value?