MOSFET RDSon

RDSon is based on a lot of factors so the data so pretty much give an estimated approximation. https://www.taiwansemi.com/assets/uploads/productcategoryfile/AN-1001_A1611.pdf is a nice resource I pulled from Google, but in short all of the a lot of factors affect RDSon (DS and GS waveforms, frequencies, voltages, & currents as well as just temperature). Often RDSon is given by graphs in the datasheet per each device which give more info and the table at the top which is just showing you some high level information. Ultimately you'll never really know the exact RDSon of a device until you test it out. It's just when sourcing a FET you need to make the best approximations to understand your system and give yourself enough margin to have a robust design.