Bring the working thread up at 1 take it down at step 2,bring it up again at step 3, then take it down at step 4 while crossing over the stitch just made at steps 1-2.
Each line represents a fabric thread
You will find that the cross over stitch at steps 3 and 4 only needs to go over the thread at steps 1 and 2 and not over the fabric threads as shown in the diagram above.
This is a charting problem that grid depictions can have. You would work stitch 1 and 2 over four fabric threads as shown here, but the stitch at 3 and 4 would only go over the thread at step 1 and 2. The stitch would be worked entirely in the space between the vertical threads.
This stitch is not really the best one for the higher count even weave fabrics. It was used extensively in Early North American Crewel Embroidery. Crewel embroidery fabric can be an even weave, but is often a tightly woven twill. This stitch would be worked between two drawn lines of a design. It was used instead of a Satin stitch because it was thought to be more economical. I would use it because it can take harder wear. A novice stitcher would find it easier to stitch.
The carnations in this embroidery were done with the Roumanian stitch
This stitch has been adapted from its original use for the crewel embroidery. A Mamluk fragment shows it used slanted across the fabric threads in steps 1 and 2. And stitched over eight or more fabric threads instead of the four I have shown here. That would make it much easier to use on a counted fabric. The Egyptians called this 'the stitch that couches itself' and then the Mamluks came into Egypt and eventually brought the stitch into Europe. ©2005, Linda Fontenot, www.AmericanFolkArts.com