The flag definition has to do with how to deal with the low and high setpoints. It is an integer field where each bit represents a different flag. There are 7 possible flags right now:
bit 0 - low exclusive
bit 1 - low infinite
bit 2 - high exclusive
bit 3 - high infiinite
bit 4 - any change
bit 5 - low driven (by tag)
bit 6 - high driven (by tag)
So if you want the alert to be in alarm if the value is negative infinity and <= 10, the flag would be 2. If the 10 is replaced by a tag the flag would be 66. Hope this helps.