mtnrox-co
The number (60/100) that you see under that Placeholder Density image in your message, is the average of your placeholder density across mobile, tablet, and desktop. If you click on that image, a panel will open that shows the individual placeholder density for mobile, tablet, and desktop. It may be that mobile density is very low (or tablet or desktop), bringing the average down. For example, you could have 98% on desktop and 40% on mobile - or similar differences.
I was able to raise my density score by going through a bunch of placeholders and being sure that they were activated for all three devices. Or at least that all three devices have a high number of placeholders activated for them. It is very easy to overlook that if we simply insert placeholders without going through and double-checking which devices they will be displayed on.