not definitive, but some thoughts
The colours are all interpreted by the spot meter as grey (at 18% reflectance) is my understanding, and the meter wants to expose them as grey. Your card indicates the typical ramge of reflectance of the color in question in the first column.
The second column I believe is somewhat un-related. It says to me to meter something with that color, measure it, but then instead of using the exposure that dials up for zone 5, use the exposure that lines up for the exposure zone given.
This makes sense on my analog spot meter. I am not sure how you tell the digital spot meter that you basically want to dial in an EV correction to adjust the exposure up or down a few zones. On my analog meter I just turn the dial to put zone 3 at the needle reading value, instead of zone 5, as an example.
I use a colour swatch out of an old kodak data guide as my test card. It does not have the range of colors as say a macbeth colorchecker, but mine came from the used bin at$3, rather than the $80 or so that the macbeths seem to always go for.