Read through this tech section to confirm you are using the correct procedure to check the oil -
https://faq.ninja250.org/wiki/How_do_I_check_my_oil%3F.
Basically, as previously noted - warm oil, engine off, balance vertical on level ground, wait 2-3 min - it should be between the upper and lower marks.
Should take 2qts with filter to get to the top mark. Check your airbox for excessive oil if everything else checks out. With extended high speed operation they will pump oil from the crankcase breather into the airbox, but it shouldn't be excessive unless there are engine problems like extreme blow-by.