It's not the only source of sea level rise, or even the major one - that I believe is expansion from rising sea temperature. So it's an
additional 1mm on top of the others, and any catastrophic glacier collapses such as may be approaching with Thwaites in the Antarctic.
The more that melts results in changing albedo and smaller thermal mass to encourage an accelerating melt - a small runaway feedback loop. Rising air and sea temperatures will accelerate it further.
You and I may not care that much - yet, but those in the Marshall Islands, Maldives and other low lying regions almost certainly care about every millimetre. Sea level rise is probably the least dramatic effect of climate heating, but the most inexorable. It takes a while to melt 650,000 cubic miles of ice, yet we seem to be managing to get going. It will accelerate.
It should be cause for major concern.