Question: what do these numbers represent? What are their units?

[jhrcek]

I'd like to ask about what do the numbers in the first 2 columns in the details section mean?

Do you think it would make sense to add units of these numbers in the table headers or some legend explaining the numbers?
This could be done e.g. by adding title attribute to table header cells. This would show a tooltip on hover as I sketched in the screenshot below.
If you agree I could do a PR (but I'd need to know what those numbers mean 😄 )

[maralorn]

I am pretty sure, that hover number over the graph is the occupied size on the heap in Bytes by the specific constructor.

The n ist I think just a running number to disambiguate different entries, but I don’t know where it comes from.

[TeofilC]

I think there's some documentation in these notes: https://github.com/well-typed/memory-usage-zurihac-2021#the-detailed-pane
It would be great if this info was integrated into the generated HTML somewhere