Are you using
Popads? Because those browsers look like they're being picked up by your tracker (
BeMob?). Popads doesn't drill down to that kind of browser level - if anything those would be in the 'unknown' category on Popads. But if you're running a push offer then you only want to target Chrome.
It depends. How targeted is your campaign? Are all the geos you're targeting green and all the publishers? Until then I wouldn't look at devices.
The trick is to go after all the big things first - is there a whole country that just doesn't want your offer (maybe they speak a different language to the one the offer is written in, so they can't even read it)? Is there a publisher site that users don't like your offer (maybe that site has really poor implementation of the Popads code so your ad loads so slow it's never seen)?
Be patient and keep testing $5 at a time then stop and make one or two small changes then test again. Repeat.