That's explained in the EQ window help:
The Target Level control lets you move the whole target response up or down until it sits in the right place relative to your measurement. When the target is right the bits that go above it are the peaks you want to tame and it usually runs more or less through the middle of the measurement. Calculate target level from response automatically adjusts the level of the target response to provide a good match to the measurement over a suitable frequency range for the target type, but don't be afraid to manually adjust the level to suit. If the target is Full range or None the target level is adjusted to align with the measurement between 200 Hz and 2 kHz. For Subwoofer targets the alignment range depends on the sub LF cutoff and the bass management cutoff. For Bass limited targets the lower end of the alignment range depends on the bass management cutoff and the upper end is 2 kHz. For Speaker driver targets the alignment range depends on the driver crossover frequencies.
