This is traditional charting for 1/4 stitches. There should be another symbol opposite the little s. Or it might mean a 1/4 & 3/4, if there's no backstitching instructions. With this combo, you get the 2 quarter stitches, and the diAgonal half takes the "top" color. I.e. sleeve or hair is on top of skin, roof edge is on top of wall.
With evenweave, go over 1 instead of 2. With Aida, get a sharp needle & poke through the center of the 4 threads between the holes.