Kontakt 5 "Impulse Response" and "size" adjustment

The "Convolution" (in the effects section of Kontakt 5) includes an adjustment (on the left hand side) for "IR Size". The adjustment is in percentages, from "50%" to "150%."

Does "50%" mean that the impulse response is COMPRESSED or SQUISHED to 50% of its original size? (So you get all of the impulse, but its TIME/LENGTH is cut in half; so a 3 second response becomes a much denser 1.5 second response.)

Similarly: does adjusting the IR size to "150%" mean that the impulse is STRETCHED or LENGTHENED to 150% of its original size? (So a 3 second response becomes a 6 second response.)

Or, alternatively, does "50%" mean that the impulse response is CUT or CHOPPED in half? And "150" mean that extra empty space is added to the end of the impulse?

The latter seems unlikely. But I'm not sure. Nothing on this in the manual.