The "Submission Rate" drop-down menu on the "My Bookmarks" and "Add Bookmark" pages controls how fast or slow your bookmarks receive social submissions. In general, here's what the settings represent:
Drip = Once per week
Slow = Once every 2 days
Normal = 2-3 times per day
Fast = 8 times per day (costs 50% more credits)
The system will automatically pause/start your bookmarks in order to achieve the Drip and Slow rates, so don't be alarmed :)
Disclaimer: there's no guarantee that the rate you set will be exactly what you receive, because of the human element of SocialAdr. These are just estimates.