I don’t have that same monitor, however the manual says it will negotiate to one of the following settings:
0.5V/3A,
9V/2A,
12V/1.5A,
15V/1A
So you’re looking at 18W max. Which probably won’t be enough to keep the laptop charged. I have a Gigabyte m28u in the mail which will have the exact same problem. My solution will be to just plug in another cable for charging.
18W might be acceptable if you A) Close the laptop lid so it’s display isn’t being used, not use any peripherals and set the windows performance slider to best battery or B) Allow the battery to slowly drain (but slower than normal) throughout the day and have it charge back up overnight.