This question is a follow up of another question I have asked recently.
For the sake of experiment I propagated the ISS's position (using SGP4) from epoch of first TLE to the epoch of next released TLE. The difference in time is a little over a day. The resulting position comes incredibly close to the one in the epoch of the second TLE. The difference in position vectors is in the range of meters. So, as strange as it may sound, instead of being happy about it, I am a bit concerned.
That result makes me wonder — is it possible that the propagation in the time span of a little over a day can be so accurate? Or is it due to the second TLE being produced from a series of previous TLEs? What is the most likely reason for my results? And what is the usual way of producing TLEs on the Celestrak website?