I'm not computer savvy enough to shrink the link.
If I'm remembering correctly, there's like a larger to smaller rule. Follow the Nucleus. In the Promyelocyte, it appears to cover the entire cell. In the myelocye, it's about half, maybe a smidgen more. Metamyleocyte it starts to indent, when you get the horseshoe, you've got a band. And finally the band indents nearly completely to give off a segmented neutrophil.
You may know the last 2, but I figured completeness for the sake of context helps.
People don't seem to like the color version as well(lol), but honest to god, the way I remember something like this is:
The whole thing is dark purple=promyelocyte.
The dark purple receeds in=myeloctye
The dark purple is indented, but less than 1/2=metamyloctye
The dark purple is almost a perfect horseshoe=band
The horseshoe now has multiple segements attached by super thin strings=neutrophil