Mike,
The "slope" is the physical property of Fuel Flow vs Injector Pulse Width.
The slope values are fuel mass per time unit (ie pounds per hour/ CC per Hour etc etc)
When the injector is operating on the low slope it tends to operate in a less linear manor. This is (partially) because the injector is operating at close to it's min pulse width. Once the injector is flowing fuel on it's high slope factors like injector deadtime (the time it takes for the injector to physically move once energises) come into play and can limit overall fuel mass delivered.
The breakpoint is the change over point from low to high. This is measured in mass of fuel as is usually the point the injector flow become linear
Injector PW minimum is the minimum PW the injector can operate at in a stable manor
There are multiple multipliers/adders that effect the final inj pulse width.
IE-
Flow v Pressue (not untilised in our cars)
Offset v Voltage (this is an adder that increases inj pw for lower battery voltage)
Offset v Pressure (as per offset v voltage but not use in our cars)
This is a very simplistic explanation but should get you started. BTW im -Luke- on AL and Hiddeous on the HPT Forum. If you've got any questions sing out. Also if you decide to go ahead and want some coaching let me know as I do this quite often
Sample of HPT basic injector data screen-