The Scheduling is basically a Process that AwareIM automatically runs about every minute. I do not think it is guaranteed to run exactly every 60 seconds. If you want to run a process about every minute, you do not really need any condition checking the time, just create a rule that calls your process.
To run a process every X minutes, you will have to somehow keep track of how many minutes have passed since the last time it ran. Since the TIME_ADD function adds hours, to add minutes you need to use a fraction. It does not matter how you calculate that fraction. To add 15 minutes, the fraction can be calculated by using 15/60 or just use .25. Both should work.
