1. Backup the original files before making any changes.
2. Open the file lib/metabox/jquery.cmbScripts.js in /event-manager-theme-functionality folder in your /wp-content/plugins directory.
3. Find (at line 34)
step: 30
This value represents the minutes, replace 30 with your desired value. For example 5 for a 5 minutes step.
4. Update the file