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.