Why would the same RAM sticks show up as 16GB in one machine but 32GB in another?

I think that's the situation. DDR4, if that matters. I tested a couple RAM sticks in one machine. 8+8. Ok. Great. So someone's getting a little more RAM. When I put those sticks in the second machine, the numbers were off. Maybe defective RAM? But then I realized it was actually 16+16 in the second machine. I may not have pressed the sticks in enough on the first machine so only one was recognized. RAM sticks were the same for sure. They didn't get mixed up with others. Is there any other explanation, like the slots used or some difference between machines, besides that I didn't push one stick in enough on the first machine? I was glancing at other sticks and saw dual channel... Would there be anything like one machine being able to take advantage of something to be double (say 16GB) another machine that can only use the base amount of RAM (say 8GB)?