SLI is slide speed, that’s the length of time it takes for the pitch to slide from note 1’s pitch to note 2’s pitch when a note slide is applied to note 2.
BND is a note bend amount dial, with positive and negative ability, which acts like a basic pitch envelope in conjunction with SLI.
Negative values bend up to the played note and positive values bend down, the further you turn the BND knob the greater the pitch sweep and, of course, SLI amount dictates the speed of the bend.