Explore's Liked You shows everyone who Liked you. This is split into NEW and SWIPED.
NEW (horizontal list) are all members who Liked you and you have yet to Swipe them back.
SWIPED shows all those members who have Liked you, and you have already Swiped them back.
This number on the Explore icon at the bottom is the total number of profiles in Explore's Likes You that you're yet to Swipe back on.
Like or Pass on these users for the number to decrease.