You can define the amount of hard drive space the Rockstar Editor can use to store clips in Pause Menu > Settings > Rockstar Editor
The length of an Action Replay clip stored is dependent on the amount of activity that has taken place during recording. In busy segments this tends to average 30 seconds, in less eventful segments this will be closer to 1 minute 30 seconds.
Clips are named automatically upon saving, in the format ‘Month DD YYYY Clip XXXX’ (e.g., ‘Jan 13 2015 Clip 0001’).
You’ll be notified if you are running out of space to store clips. You can visit Pause Menu > Rockstar Editor > Clip Management to delete unwanted clips and free up more space.