Do you just not want this notification to happen if the hub is in Manual mode? If so, a rule like this should work:
Note that "IF (Mode is Manual) Exit Rule" is is made by choosing "Simple Conditional". The IF (TEST Garage Door open) THEN" is made by choosing a full conditional, i.e., "IF (conditions) THEN," as seen in the dropdown when adding actions. You could use a full conditional for both as long as you properly format them (including an END-IF), but it's more clicking, so I wouldn't.
This is basically the rule I had above, plus the mode exception, and it will also turn the siren off when the door is closed (you may not need to do that; it depends whether your siren sounds indefinitely or stops on its own--and, of course, whether you want this to happen). If this is what you want, your final rule should look more or less exactly like this except for the device names (and the device states in green or orange--just RM trying to be helpful by showing you the current truth evaluation).
(Note: This won't stop the siren--or stop it from happening after the delay--if the hub is in some other mode and then changes to Manual mode after it's opened. There a few things you could do to prevent that if that's a dealbreaker, but since there seems to be trouble getting even this far, I'd recommend starting simple.)