What does 'source of' mean on a label?
A label can't just claim there's a lot of something in a product. There are rules for that.
Source of
A product may call itself a 'source of' a vitamin or mineral if it contains at least 15% of the RI. For peppers, that's per daily dose.
High in
'High in' only applies at double that: at least 30% of the RI.
Why it matters
That way these words mean the same everywhere. Health claims are only allowed from that 15% too. Read more in why we say contributes to.