First off, different phones are different, and some phones will work better than others. This is why the "set this for me" option in sensitivity may not do the trick for you.
Once you get things setup and working for you, RangeTech will remember you settings and you are usually good to go from there on out, but some phones/situations may require adjustment and a bit of trial and error to get things working.
If "not-shots" are being detected as shots:
Such as falling steel, reloads, etc. Move the sensitivity slider towards less sensitive.
Keep in mind that dropping or bumping the shot timer is going to be very loud to the sensor no matter what, and, just like most other shot timers, can cause false shots.
If extra shots are being recorded during shooting:
For example, you fired 4 shots and RangeTech says 5 or 6 or anything more than 4. Move the sensitivity slider towards less sensitive and give it another try. Repeat if neccessary. If that does not do the trick, increase the anti-echo setting slightly, perhaps 0.15, and give it another try.
If some shots are being missed:
Move the sensitivity slider towards more sensitive, and/or move the shot timer closer to the shooter. Also ensure anti-echo isn't set especially high (0.11 is default and works for most situations)
If a nearby shooter is being picked up:
Move the sensitivity slider to less sensitive. Keep in mind that RangeTech is not magic and there are limitation here, as with any other shot timer. For example: If someone is shooting a 9mm in the next stall at an indoor range, you probably aren't going to be able to pick up your rimfire gun without getting his shots as well.
If close-together shots (fast splits) are not being recorded:
Lower the anti-echo setting. You can think of this as a "minimum split time" as that is basically what it does.
Of course, if you are still having issues, please let us know so we can help you, and we can recognize ways to improve the app!