Something is wrong. If the output is between 1500 e 2000 Hz it cannit drive from 0 to 3000 Hz.

Is it a combination between step of 500 Hz and the fine tune between the two limits?

Pietro

See User Guide 4.2. Radio and Split Operation bullet point
or simply there are two frequencies that define the output frequency of your rig. The first one is the red goal post frequency and the second is the VFO frequency. When the goal post is between 1500 and 2000 Hz, then the VFO is as indicated in the frequency display of wsjt-x. E.g. goal post is 1600 Hz and VFO 14074 kHz, the actual output freq is 14075.6 kHz.
Now when Split is applied the actual audio frequency is moved into 1500 to 2000 Hz range in 500 Hz steps and VFO is "corrected" in opposite direction in 500 Hz steps. E.g. goal post is 2100 Hz and wsjt-x shows 14074 kHz, then the audio will be 1600 Hz (not shown to the operator) and rig VFO will be 14074.5 kHz (not shown in wsjt-x, but shown on the rig VFO) resulting 14076.1 kHz as it should be.

73, Reino OH3mA