A few of my teachers who'd used +/- signs added them to differ between a strong qualification of work to the grade and a one step for higher/lower grade respect

A few of my teachers who'd used +/- signs added them to differ between a strong qualification of work to the grade and a one step for higher/lower grade respectively, i.e. 3- converts to "almost 2", which is just a written clarification. I saw once a 2+!