Pcb diagram symbols and abbreviations

Based on what I see on Apple diagrams, those seem to refer to dimensional constraints on the board.

For example some components have to exist in a defined physical location, because other components have to interact with it, or some components have to stay in a specified region, for example due to RF or power isolation.

In your example, the test points have to present in a defined layer and area on the board, because the test fixture has to be able to connect with it, the standoffs have to exist in a defined area because the phone case dimension and screw post positions have been defined by some other teams, and the layout guy can’t change that.

Those are just guessing anyway.