We use prefixes before units of measurement to signify that the value is multiplied by 10, or 1000, or 0.01, etc. We do this to avoid adding lots of zeroes if the number is particularly large or small.
There is a international system for this:
Prefix | Number |
k (kilo-) | 1,000 |
M (mega-) | 1,000,000 |
G (giga-) | 1,000,000,000 |
da (deca-) | 10 |
d (deci-) | 0.1 |
c (centi-) | 0.01 |
m (milli-) | 0.001 |
μ (micro-) | 0.000001 |
n (nano-) | 0.000000001 |
You can find the full list for this here.
For example, a centimetre (cm) is 0.01 metres (m),
a megavolt (MV) is 1,000,000 volts (v),
and a millisecond (ms) is 0.001 seconds (s).
In your example, 4.6 kl would be 4,600 l.