What is the equipment? Sounds like maximum ambient air or possible air temp of air dryer or something. The equipment needs to be known.
Some mfg's come up with some not so standard specs which can only be defined by them.
I'm guessing that means that the max service temperature when used in an air environment is the listed value. The material is probably used in other environments as well, and may have different service temperatures in those cases (in water, in nitrogen, etc).
Temperature affects many properties of materials, and at different rates. Mechanical properties may be your main interest, but others may be more drastically affected. You can find some material properties for polyurethane on