It is more important for your conditions to be stable, even if they don't quite fall inside the lines of the vpd chart ..... If you are close, just keep looking til you find a different chart where your numbers fit in (I've seen several versions)
"keep looking…" - that's horse before the cart.
VPD charts for have different values because optimal VPD values are different for different stages of growth. VPD makes it easy to
understand how to change the grow environment to improve the outcome of the grow.
Real life example - my 2' x 4' tent is in an unheated garage in Southern California. For my grow this Spring, I used AC Infinity equipment to keep VPD at 0.8, 1, and 1.2 for seedling, veg, and flower. It's not easy for me to control temperature so I control RH to keep VPD ≈ optimal.
Prior to this year, I had an Inkbird RH controller and I had to check RH multiple times per day to keep VPD in the optimal range. It was a PITA to do that and, when the AC Infinity finally released their humidifier, I retired the Pulse and used the Controller 69. Thanks to the mostly mild, very predictable (cool) temps that we've had for the past couple of years, the C69 was able to keep VPD in optimal range almost 100% of the time. The C69 is, arguably, the most valuable piece of tech in my tent.
Keffka has posted about keeping a grow in "balance". I agree with his premise completely. This text from a web page for what I believe to be the hands down best value in lighting for a 2' x 4' grow tent* - "Recent studies show that PPFD levels as high as 1,500 umols/m2/s will deliver a proportional increase in yields so long as other critical inputs are kept in balance. These include CO2, water, and nutrients."
A grow that has VPD (which is just a proxy for different combinations of temp + RH values) in the optimal range just means that the temperature and RH will allow cannabis to thrive. That still leaves (pardon the pun) plenty of other
opportunities for growers to screw up their grow areas to address to optimize their grow. To that end, I've posted a screenshot from one of Bugbee's videos:
VPD is a good tool to keep RH and temp in range but the other issues need to be dress right dress to maximize the quantity and quality of the crop.
*spetrum-wise it's a $280 knock off of my $640 Growcraft flower light and it's got the best PPFD map I've seen on any grow light