What's the upper bound on several?

Ten, a hundred, a thousand?

The meaning of several, as reinforced by community usage, to me means "<=10".

I may have several points to make, but I feel obliged to tell you specifically if I have 10 or a dozen or more to make so you can find a chair. ^_^

For >= 10, we have dozen, baker's dozen, score, and 20. This completes the set of conversational units of vague quantities.

I think I expect all of those to be more or less accurate (for the >= 10 ones).

If someone says a dozen, I would expect exactly 12 (especially if it’s something with very strong collocation like “eggs”). If someone says “a baker’s dozen” I would expect exactly 13. If someone says “score”, I’d be surprised, but given how infrequently it’s used, I’d expect the speaker to be using it accurately, not sloppily.

What about a bunch?

A bunch of grapes could have many dozens of grapes. Perhaps even a 100 or more.

There's a cereal called "Honey Bunches of Oats". Maybe that word can veer off into non-numerical quantities.

what is a non-numerical quantity?

In the above, "honey"

but a "bunch of" is an actual measurement: a bunch of grapes, a bunch of wheat

No upper bound since it also is often used as understatement.

This is exactly how I use them.