The significance is not the number. The significance is that the avian flu jumped from avian species (birds) to a mammalian species (seals). It's one evolutionary step closer to infecting humans and livestock.
Covid-19/SARS2 started with a couple of "pneumonia" cases in Wuhan during late Autumn, 2019. Possibly even started with 4 infected workers cleaning a mineshaft in Yunan province, China, in 2012. It presumably jumped from bats (to an intermediary mamalian species and?) to humans.
The 1918 Spanish Flu started with one infected man from a Kanasas farm.
SARS1 evolved in bats, jumped to civets, then to humans. It was contained before it evolved to become even more transmissible among humans.
In the early 2010's, Ebola jumped from bats to a few humans in West Africa. This eventually led to a handful of human infections in the United States.
If the avian flu that is currently circulating along the south and central coasts of New England can jump to seals, what other mammalian species could it jump to? New England shorelines are populated with mammalian scavenger species such as coyotes, racoons, rats, feral cats, and possum. If one of those species comes into close contact with an infected seal, dead or alive, that species could become a new vector for virus spread, evolution, and eventual jump to humans and livestock.
This development needs to be closely monitored by NOAA, USDA, and CDC. It could be an emerging health and economic threat to humans. If adequately monitored and contained, it will become a forgotten anomaly. If not, anything is possible.