JEECE

Percentile scores, basically, tells you how you have performed relative to all other candidates who appeared for the exam. It is not the same as your percentage score. While the percentage score tells you the percentage of the total marks or maximum marks for the exam that you have secured, the percentile score indicates what percentage of the total number of candidates appearing for the exam have scored EQUAL TO or LESS THAN the score you secured. This means, in each session, the marks secured by the candidate (say, out of 360 in the case of JEE Main Paper 1) is converted into a scale ranging from 100 to 0. The topper for each session will, thus, secure a percentile score of 100. he Percentile Score for JEE Main will be calculated using the following formula:
Percentile Score of a Candidate = 100 x (Number of candidates who secured a raw score (or actual score) EQUAL TO or LESS than the candidate) / (Total number of candidates who appeared in that session)
You can get more information here in detail - https://www.shiksha.com/engineering/articles/how-to-calculate-jee-main-percentile-score-know-normalization-process-blogId-19933.

Starting date of 2nd round of counselling: fourth week of July 2018.
2nd Round Of Counselling-
Candidates who have got admitted through the 1st round of counselling may also participate in the 2nd round of counselling to change their course or stream and institution. The process of seat allotment will be carried out until all the seats are filled. Government specified reservations will be applicable on the seat allotment. In case a candidate is dissatisfied with the allotted seat in the first round, then he/she can opt for seat upgradation in the second round. If the seat is not upgraded in the second round, then the first seat allotment will be considered as the final allotment. After successful seat allotment, candidates will have to confirm their admission by reporting in person to the allotted institute and completing the requisite admission formalities.