Yes sir i understan your problem related to this so i would like to give you brief about it as follows:

To become eligible for NATA a candidate is required to fulfill a certain set of eligibility conditions. Mentioned below are the predefined criteria set up by COA:

• Candidates must have obtained 50% aggregate in Physics, Chemistry and Mathematics and also overall 50% aggregate score at 10+2 level. 
• Candidates who have passed any 10+3 diploma exam with Mathematics as a subject and scored at least 50% marks are also eligible to apply for the exam.
• Students appearing in class 12 with Physics, Chemistry and Mathematics are eligible to appear in NATA, however, their result will be declared valid after fulfilling the above criteria.  
• The marks cannot be rounded off, as if the candidate has secured 49.9% marks in his/her qualifying exam then the marks would be counted as 49.9% only.
• The lower age limit for appearing in NATA has been waived. However, the candidate has to comply with any age constraints that may be specified by respective Counselling/ Admission Authority.
• Score of NATA 2019 is valid for a period of 12 months i.e. 1 year from the date a 

To upload your marks to the nata, you need to login to the nata official website, sign in to your account and enter the marks manually besides the subjects. And then you will have to upload the scanned copy of the your marksheet, and do adjust the dimensions.

Good luck