Hello, 

The ranking is decided on the basis of the percentile score of the candidate. Now percentile score means your performance with respect to the performance of the other candidates. It might be possible that there are many other candidates who have scored same or higher marks than 551 (your score). Also while deciding the rank, the candidates getting same marks will be given rank on the basis of individual subject score i.e. suppose if some candidate has scored higher marks in Biology section of NEET then he will be given first preference in the ranking system. This is how basically the ranking system works. If your rank is 23300 there are chances that there must be many other candidates who have scored 551 and above marks or they were given preference because of their Biology section marks in NEET.

Hope this helps.

Good Luck.