Capacitor value in schematic with "mk" units
Some languages do not have the µ letter on the default keyboard and use mk as abbreviation for mikro. 1µF and 10µF are typical sizes for "big" blocking caps.

Using just n for nanofarad and pF for picofarad provides a stronger optical difference between these units. Most caps in a digital circuit are expected to be in n range (small blocking caps), you want the shortest form here with just one letter.