OP, just for a bit of side info:
Your watts are the number you get when you multiply volts times itself and divide by resistance(ohms).
3.822 / 0.47 = 31.047
When you adjust the watts in variable wattage mode, your device automatically adjusts the volts based on what it reads your ohms to be so that it gives your desired Watts.
For example, I am using the 60watt version of your MVP and my Ohms is is currently at 0.56. So, if I wanted to use the same 31 watts as you, my MVP would automatically set the volts at ~4.16. Because 4.162 / 0.56 = ~31.
I only point this out because I noticed you said 28 watts and 3.82 volts. If you turn your watts up, the volts go up accordingly so that the volts number can be squared and divided by the ohms inside your device. Your MVP does this all by itself. Wattage mode is sort of like cruise control(that's a good thing, especially for beginners =)). It makes it so that, no matter what your coils resistance(ohms) is reading, it will automatically adjust your volts for you so that you always get the watts that you desire.
So, say your next new coil reads at 0.51(I'm assuming your coils are marked 0.5 ohms. Coils vary slightly in how they read. This is normal and nothing to worry about unless you have a 'large' difference such as a 0.5 ready 1.1 or something), your MVP will say 'oh, this coil is 0.04ohms more than the last one. I had better adjust the volts for him!'
It's a long reply to you but I hope it helps, since knowing this stuff is very useful. Especially if you get into mech mods in which the only way to change watts is to use difference ohms in the coils one builds.*