Since all of my sap flows directly to the sugarhouse and I do not use a meter to measure how much sap I have, mine is just an educated guess. I do measure the sap sugar %. My most important number is simply how many gallons I produce and how many taps I had to achieve that.
Unless we start to have more freeze thaw cycles I will not even be close to my last 2 yr average of 1/2 gal syrup/tap. If it stays like what I've had so far I might be lucky to do 1 qt per tap. I've only had 3 real good flow days. Yesterday was slow flow as the temperature climbed to 72 in my sap tank and I processed within 90 minutes of it hitting the tank until the incoming sap got to 70 F. I then shut down. Looks like a freeze tonight, that will help.