The metric PERCLOS (percentage of eyelid closure) is calculated by counting the number of frames in which there was no pupil detected, and dividing this by the total number of frames for a specific time interval (task or entire recording). Therefore this metric is available only as a single value for a certain time period.
If you export the raw data (File > Export > Data): you will be able to output the pupil coordinates, size, height, width, etc. for each frame of your data recording/task in a text file. In this export, you will see that the pupil values are 0 when there is no pupil detected (i.e. blink) – this allows you to determine whether a frame contained a blink or not. You could also use this information to calculate the blink rate or PERCLOS.