Table 1 tells us that there were 6 total Omicron-period deaths while hospitalized in the fully vaccinated group. It is almost certainly a single death. It's conceivable that it's two deaths, but more than that appears mathematically impossible.
Unless I'm reading the report wrong, it's from a single hospital. We shouldn't be taking any lessons from such a limited dataset as there are far too many possible confounding factors that would be ameliorated in a larger dataset from more hospitals.
Unfortunately the study authors didn’t provide the underlying data that created the figure in a consumable format, so it’s hard to draw conclusions.