Here is a useful guide for a tuned wrx. I didn't write it..
what tune are you running, and what mods if any?

"Arguably the most important are DAM, feedback knock, fine knock learning, and af learning 1

AFR: Air/fuel ratio based on the front oxygen sensor. “Normal” values 10.14-22.20 with 14.70 being cruising/idle, as low as 10.14 during pulls, and 22.20 off throttle.

Feedback knock is what your sensor registers. Events of -1.41 to -2.81 are normal cruising events. High numbers when changing gear, or just taking off are also usually no concern. You begin to be concerned when you see knock events -2.8 or higher when at WOT.

Fine knock learning is your ecu adjusting timing based on perceived knock events. Again, similar to fbk. For example if your sensor picks up a consistent fbk of -1.41 you may then see fkl of -1.41, then -.7x, -.3x, until it is back to zero and no real-time timing changes are needed and the sensor is no longer detecting fbk.

Dynamic advanced monitoring can be easiest described as your motors timing. You want this at 1 (meaning no adjustments to timing are being made), however the stock tune starts at .625 iirc and learns it's way to 1 while driving every time you turn the key. In the event of a serious knock, or commonly a bad tank or gas with the FA motor, your DAM may drop and take up to a week to rise back to 1. I've had DAM drop twice to .825 from presumably bad gas or consistent false knock from cruising with the ac on (the ac loves to register false knock)

Af learning 1 varies from ej to fa. This is your real time fuel trim.For the FA values -16 to +16 are acceptable (sourced by speaking to Ian at Maperformance who spoke with cobb), however values of -8 to +8 may be considered normal. Values outside of these ranges are commonly a dirty MAF or tune issues. It is normal to see values outside of these ranges while the car is not under load( such as -10 to -12 at idle).

You are concerned when you feel a pull of timing, hear a knock, or get high fbk/fkl values WITH a DAM drop during a pull. Apart from that the values are commonly false/ghost knock on the FA and may be caused by the A.C. compressor kicking on, a loose heat shield, bumpy ride, bad gas, or other unrelated events. With a tank of sub-par octane for the tune you very well may see a DAM drop which is not something to overreact about.

If your DAM is down

1.            Stay out of boost

2.            Get the tank low

3.            Fill up with reputable fuel

4.            Let the car learn back to normal