3 week progress, seems behind schedule

I planted my first auto flower about 3 weeks ago in the windowsill (over 8 hours of sunlight a day) and it seems to be healthy but significantly smaller than anticipated at this stage; I thought the stem would be hardened off by now and nearly ready for transplanting out of the jiffy pellet. There is a root pushing through the pellet, if that means anything? How’s it seem to you guys?

It’s in need of a transplant.