Analyses of Fertilizers

In the analysis given on fertilizers/supplements such as those in
garden stores, is the breakdown by mass or volume?  For instance, I
just bought a supplement containing 4.60% Fe.  Does this mean 46000
mg/L, or 46000 cc/L?

As long as I'm here...  0.2 mg/L is the Fe level the PMDD shoots for,

Thanx much,

Brian T. Forsythe
crom at cris_com

Every picture is not worth a thousand words; besides, I think I'd rather have the thousand words.