Fact: growing embryos generate (some) heat of themselves. I have two Brinsea oct. eco bators with 20 and 21 eggs in each.......IOW, almost full. I don't know if the eggs are acting as thermal mass or it is the developing embryos, but the fuller bator seems to run a bit warmer than one that has just a few eggs in it. I recently did a run with 5 eggs in each bator, and it didn't seem that the eggs/embryos affected temps much.............. The development i am seeing now in the embryos in these NEARLY FULL bators seems much more advanced than the embryos i had at the same age in bators with only 5 eggs in them. These embryos just seem to me to be a bit ahead of schedule. Both bators were calibrated by Brinsea Spot Check therm to 99.5 at mid egg level beneath bator fan. Also even with RH at 40-45 %, at just day 7 the eggs seem to weigh too little if you need me to explain myself more, i can.