That means according to your MMR you are placed ABOVE your skill level, so the LP is trying to force you to be towards the ELO/MMR it feels you belong in. For example, according to na.op.gg you are at 597 MMR, your current ranks averages is 780. So as a whole the system is trying to correct what it feels is a mistake in placement, same reason at the start of a season/smurf you may notice high elo players place silver/gold and skyrocket, because their MMR is high because of how they leveled, the ranks they played against, how they performed in those games and tons of other factors the public doesn't know.