Error: The sum of volume fraction exceeds 1 in some faces
 

I'm performing a three-phase simulation using VOF (explicit method) with species transport method in synergy.*
All three phases are fluids (liquid steel, slag, and argon).
I'm patching them one above another like immiscible fluids.
Initially, I've liquid steel in the whole vessel and after patching I want to have liquid steel (427mm) at bottom with volume fraction of 1,* middle layer with slag (10mm) with volume fraction of 1 and top layer of argon (40mm) with volume fraction of 1.
I'm getting the following error while patching slag with volume fraction 1.

Warning!! The sum of phase volume fractions exceeds 1 in some cell(s).
This can lead to potentially erroneous initialization. Please insure that the sum of phase
volume fractions in a cell does not exceed 1 during intitialization or patching!!