The Test Tracking feature is extremely easy to use. The window has one line per each line. Lines that are grayed-out are below the horizon and cannot be used. Double click any line that is not grayed out to test out tracking of the target at that time.

When you double-click a line you will be prompted for with a confirmation dialog. If you click OK the scope will slew to the target position and start tracking. Horizons uses closed-loop tracking, which means that it checks and adjusts the RA and Dec to make sure it matches the RA/Dec coordinates of the object. You can disable this be clicking Disable closed loop corrections. If you do this the tracking rate will still be constantly adjusted to match the target's rate but you can then recenter the scope without Horizons interfering and recentering the target.

To stop tracking click the Stop button.

The Status Information window shows the following information:

Test Time - the simulated time at which the target will be located at the current RA/Dec scope position.

Elapsed - Elapsed time since start of the simulation.

RA Rate - the scope's current RA Rate.

Dec Rate - the scope's current Dec Rate.

HA Expected - the expected hour angle position of the target.

HA Delta - the difference between actual and expected position. This can vary slightly because  the mount's position cannot be continuously and instantaneously polled.

Dec Expected - the expected declination of the target.

Dec Delta - the difference between actual and expected declination. This can vary slightly because  the mount's position cannot be continuously and instantaneously polled.