What does solubility limit mean in practical terms? I am not really a chemist guy so please bear with me. Glycerol monolaurate has an upper limit of solubility in water of 20 μg/mL, which is enough for my experiment. Does this mean that no matter how much glycerol monolaurate I add to water the concentration will always stay at 20 μg/mL? Glycerol monolaurate is in powder form so does this mean that the powder would flow on top of water and the concentration of 20 μg/mL glycerol monolaurate would be in the water below?

Thanks.
Q1) If 20 micrograms / ml is the upper solubility limit and you added less than 20 micrograms the solution could be less concentrated but a concentration higher than 20 micrograms / ml H2O can't be achieved.

Q2) No more than 20 micrograms of glycerol monolaurate will dissolve in 1 ml of water so if more than 20 micrograms was added the remaining undissolved powder would stay separated in some way (eg. precipitate) which could be filtered (as @MaxW has stated), or a colloidal suspension could also form. If more than 20 micrograms / ml were to be used the supernatant (GML/H2O layer) could be estimated to be 20 micrograms/ml) after filtration.