Ok, on the below picture, you'll see in the bottom left of the screen (screen not picture rotate your head if needed
) There is a 0.00Ω, that's your ohms which is your resistance level. That should read 0.50Ω with your tank on there, or at least something close. If it's not remove the tank from the device, then hold down the firing bar for a second (it'll flash check atomizer) then put the tank back on and fire it again, it'll ask if it's a new coil, hit the button for "Y" and then check that resistance again. If the "0.17" you mention is that resistance level and it doesn't change after replacing the tank like I said, try a new coil as you may have a tweaked wire in there causing a lower resistance to be read.
The big number in the middle will be your wattage.
As for what you should be using, well that's between you and the coil. Each coilhead has a range it's able to perform well in, too high of wattage and you'll end up with burnt cotton, too low and maybe it doesn't vaporize the juice. Just fiddle with it until you enjoy it. Personally I'll regularly adjust my wattage up and down for various reasons.