Starting with SFCs

I've been using Ignition for years but have never needed to use SFC's until now (I think). Not looking to have anyone create an entire chart for me, but hoping that some input will get me started in the right direction and help me understand how these things work.

I've got a tag that increments when certain events happen that I call alarmCount. I want to use an SFC to monitor the tag and if I get so many counts within an amount of time, say, an hour, I want it to notify someone, but if an hour elapses with no additional counts I want to remove one count until the count goes back to zero.

Now this is just the tip of the iceberg with regard to how I want the SFC to function, but its enough to get me started.

The issue is that, right off the bat, I'm not sure what to do. I've created an SFC with a chart parameter called alarmCount and I've set its default value as a tag() function to read my actual alarmCount tag. I have nothing on the chart itself be the BEGIN and END, and when I start it I am asked to enter the alarmCount value. Shouldn't the default value be equal to my tag value? If I enter 0 then it shows alarmCount value = 0, but that's not the value of my tag!

Any input would really help. I think that with just a small piece of understanding I can unravel the mysteries of the SFC, but until then, I'm just scratching my head!

Thanks in advance!