The relevant spec text says:

Percentages resolve to zero when specified against a content-based size [...]

It's unclear to me what that means for calc()-expressions with percentage terms. For example, say we have an inline-grid with two columns, 50px each, and grid-column-gap: calc(10px + 20%).

My interpretation is that 20% ("Percentages") resolves to zero, and thus the gap resolves to 10px during intrinsic sizing, and thus the inline-size of the container is 110px. Is that correct?
Or should the entire calc()-expression resolve to zero?