Two students pull the dynamometer in opposite directions with forces of 50 N each. What is the dynamometer reading?

This problem is solved without calculations. The dynamometer reading will be 50 N. It would seem that the dynamometer reading should be twice as large. But let’s imagine that instead of one student there is a wall and a dynamometer is attached to it. The student pulls it with a force of 50 N and the dynamometer will show 50 N. The same situation when the second student acts instead of the wall.