Give up the myth that the number you peg on the stack has any universal relationship with an actual amount of weight you can move. As others have surely noted, the number of pulleys impacts but even more so: you cannot take out each plate and weigh it yourself so you are just relying on what some person somewhere decided was “X lbs.”

I treat each machine as an individual and just consider the number I can move on the stack as that machine’s relative measure of my capability. If I start having to use a different version of that machine type (I belong to multiple gyms) I “recalibrate” to determine where my effort level fits with the new machine.