I discovered that I'm getting a richer color, more burgundy, although my henna glosses fade. vThey also tend to get a bit bleached in the sun, but this could be different for you. Henna doesn't build up for everybody.
If you've only done one glossing yet, I don't think that you'll see a big difference on a strand test. I'd wait and see if the gloss fades. When it starts to, I'd to the next glossing. You'll notice a color change, but since it's only very subtle highlighting it might take a few glossing to build up.