A quick test... pieces of paper (printer type). Cut a couple of quarter inch /1cm strips, pour a bit of each liquids on a side of a plate (just a small spoonful), and put the paper down, with just the tip (about 1cm/ 1/4 inch) in the liquid
PG soaks in paper quite fast. VG takes forever, barely soaks in paper.
You should see a difference between them.. if the "99%" VG soaks faster than the 70/30, you'll see it easily. If either of them barely soaks into the paper at all after a few minutes, odds are that it's be the 99% VG one.
Could it be possible that they simply flipped the labels upon shipping?