You are on a VFR cross-country flight from EGMD, (QNH 1029mb) to EGPG (QNH 1015mb).
Due to the persistent ache in your left ankle (which has been counteracting the en-route drift) you forget to reset your altimeter.
On arrival at PG will your altimeter,
a). Under-read.
b). Over-read.
c). By how much?