The top skin is precipitated calcium carbonate. It can clog stuff like pumps. The bottom slurry is precipitated impurities and undissolved kalk. Dosing it can clog things, add impuities and /or add to much kalk at one time.
It can hold it's strength in a still reservoir ( buckett, brute can. etc.)) for several weeks without stirring.It needs a vigorous stirring when added to the ro water and about 2 hours to settle before dosing. The dosing tube should be a couple of inches from the bottom to avoid dosing the slurry.