They do not disclose the amounts (nor do most maltsters). But I would assume 5% or less carapils and/or crystal.
Muntons Extra Light DME (37 ppg / 2-3 L) contains English 2-row (not Maris Otter) and English Carapils.
Muntons Light DME (44 ppg / 4-5 L) contains English 2-row, English Carapils, and Light English Crystal.
For a comparison, pure English and American 2-row is typically 34-37 ppg / 2 L.