I'm using a cylinder with cap fill type set to nothing. I usually add solidify to get the cylinder wall depth. I've been calculating it by knowing that a value of 1 completely fills in the cylinder.
However now, for no reason that I am aware of, it has started working in two different ways. If I open a new blender file it at least gives a predictable result. The value for thickness is the "radius" of the cylinder wall.
But on the file that I've been trying to work on it's pretty much just totally random or I'm too tired to figure out what's going on. 9.6cm=4.9mm or about 1/20th. I had set
Display > scale to 20 but I've used solidify many times in this same way and it worked as expected (where a value of 1 fills in the cylinder). As you can see I set the scale to .05 to try and compensate but that didn't do it and I'm out of guesses.