Oil Consumption During Break-in?

[Gumby 1100_imp]

I would assume that a small amount of oil might be consumed during the break-in period with the CB, but how much is normal?

I did the first change at 600miles/1000km and now have 2300miles/3700km on the same synthetic blend 10w30 oil.
NOTE: This is not intended to be an Oil Brand or Viscosity Grade Thread

During this interval the oil has dropped 2-3mm in the site window (or from just above the maximum line to just below the maximum line).
There has been no need to add any oil, yet it is clear that a small but discernible amount has been consumed.
I take these readings on the centre stand, the morning after each ride, with the bike parked in the same position.

Is this typical? Has anyone's CB burned more or less during the first few thousand miles?

Thanks in advance!