Actually this tuner is extremely accurate and can show 1 cent/halfstep offtune.
Probably too accurate.
Here's what you can do:
-first thing is to have the tuner preset calibrated for guitar. Set lownote to D2 and leave Highnote to E6. This sets the proper range for the guitar.
-CAL(ibration) should stay on the frequency used for reference A4. Generally 440Hz is used and should only be changed if you are playing in sloghtly offset tuning. It happens in studio recordings with reeds.
-make sure you have a good input level to Eclipse, blinking on the yellow leds.
These advices help having the pitch detection optimized to your instrument.
You'll finally only need to use the -I+ meter bar. The string will be in tune when the meter bar is half lighted with its right edge hitting the very center.
Repeat tuning by playing a single string several times as its initial part of level envelope is what the tuner uses best for pitch detection. When the sound of the string decays it may not be very precise.
all the best