'Slight aniso' is short for 'slight anisocytosis', which the technologist uses to describe finding varying sizes of red blood cells in the slide made of your blood. Sometimes, anemia can make some red cells a little smaller (and lighter pink on the slide). There are some normal ones, too, making a mixture of sizes, thus the comment 'slight aniso'. Just an observation, nothing dire. Don't worry. Hugs to you.
