Looks like a highly-advanced design that you can set up close enough to your muzzle so that it gives you adequate time to run up and tape the velocity number on the front of the unit.
At $14.00 why not buy one and review it (I didn't see any reviews)? That's the cost of just a few rounds of ammo--what's there to lose?
PS--I noticed with all the new small chronos out there that labradar has drastically reduced the price on it's original model--much less than the new units. Yes they are a big pain to set up and have idiosyncrasies--but they still have an enormous amount of capability and data-harvesting capability when everything is just right. When I shoot 22lr I connect the wire trigger cable, the only drawback is that occasionally it will "track" closing the bolt if too sensitive a setting is used.