90% line in JMeter aggregate report....!

The 90th percentile response time value is the value for which 90% of the data points are smaller and 10% are bigger.
To calculate the 90th percentile value:
1.Sort the transaction instances by their value.
2.Remove the top 10% instances.
3.The highest value left is the 90th percentile.
Consider the below example:

There are 10 instances(response time) of transaction “sampler10” with the values

10Sec,5Sec,3Sec,9Sec,4Sec,3Sec,1Sec,7Sec,2Sec

Sort values from best to worst:
1 sec,2 sec,3 sec,4 sec,5 sec,6 sec,7 sec,8 sec,9 sec,10 sec

Remove top 10%, in our case i.e. value “10 sec”
1 sec,2 sec,3 sec,4 sec,5 sec,6 sec,7 sec,8 sec,9 sec

The highest value left is the 90th percentile value i.e. “9 sec” is the 90th percentile value.