The unit of the capacitance is Farad, abbreviated, as F. But F is usually too big to use in electronics, so the micro F, µF and pico F, pF are often used. 1 µF=0.000001 F, and  1 pF = 0.000001 µF.

The capacitance of a capacitor is indicated as a value in µF or in pF. The number in pF is usually too long, so a 3-digits annotation is used. The first two digits represent a two-digit number, and the third digit is the number of zeros to be added after the two-digit number. The list of the capacitors used in the Tube Mic DIY kit are:

 Symbol Value on the Schematics Numbers on the Capacitor C1 1µ/400V 400V,  1µ C2 1µ/400V 400V,  1µ C3 0.022µ/630V 223 ( = 22 000pF = 0.022 µF) C4 1000P/630V 630V, 1000PF C5 0.022µ/630V 223 ( = 22 000pF = 0.022 µF) C6 100µ/25V 25V,  100µF C7 0.1µ/63V 104 ( = 100 000pF = 0.1 µF) C8 1µ/250V 400V,  1µ C9 0.1µ/63V 104 ( = 100 000pF = 0.1 µF) C10 0.1µ/63V 104 ( = 100 000pF = 0.1 µF) C11 1000µ/10V 10V,  1000µ CF Not shown 2.5 ( = 2.5pF)
You may see each capacitor has a voltage value, which is shown on some capacitors, but is not on others. Either shown or not, this parameter is a very important one. This is the highest DC voltage under which the capacitor is allowed to work properly. If you put a capacitor with a low voltage in a place on PCB with a higher voltage, the capacitor will mostly be damaged.