The "DGM" on the monitor may mean Digimate who are a TV and monitor maker selling, apparently, only in the UK and Australia.

There are other "possibles" but that seems the most likely of common icon/acronym/logo usages.

Better identification of the monitor would likely help, and on the monitor case there should be a manufacturer and model number that you could pop into Google. These bits of information are mandatory for products sold in the US, so they're likely there for UK/AUS products as well - likely on the back of the monitor itself or on the stand. Sometimes they'll be on the bottom of the "foot" that the monitor sits on.

If Google can find a maker's site, look for a "support" area at the site, and you should find what you need to know, except - - -

The only "helpful" information I found at Digimate was "see your manual for instructions." Unlike most, they do not appear to offer downloadable manuals/setup instructions for those who've misplaced theirs.

I looked at the UK site. Their separate AUS site might have something more helpful.

The Digimate site does indicate that most adjustments are "on screen" so their monitors apparently come with a program of some sort, probably in monitor BIOS(?); but they don't say anything about how to turn it on.

There likely are some switches, knobs, or other gizmos somewhere on the back or edges of the monitor, and if you can find them the technical method known as "twiddling with them" may offer some improvement. One of the buttons - assuming you can find them - likely will turn on the "on screen adjuster" but methods for using these programs are quite variable, so the advanced method of "poke, twiddle and tweak" probably will needed.

John