(a) explain the menaing of the statement electric charge of a body is quantised
(b) why can one ignore quantisation of electric charge when dealing with macrosocpic large scale charges

Explanation

(a) Meaning of "quantisation of electric charge" is that electric charge possessed by a charged body is always equal to positive or negative integer multiple of elementary charge `e = 1.6 xx 10^-19` (which is magnitude of charge of one proton or one electron).
Electric charge possessed by any charged body can have following specific discrete values only.
`q = +-e, +-2e, +-3e, +-4e`,......
`therefore q = "ne"`
where, `n = +1, +-2, +-3, +-4`,.......
Equation (1) is mathematical presentation of "Quantisation of electric charge".
(b) When a body possesses very large amount of electric charge, q = ne is very large. It means that n must be very large as e is very small. Thus, no. of protons or no. of electrons would be enormous almost countless. Hence, discreteness gets converted into continuity. It is something like when we consider a glass of water, we may be interested to find total no. of water molecules but naturally when we think of water in a big lake, it would be meaningless to think of no. of water molecules.
Hence, in fundamental discussion, no. of charged particles are much more as compared to magnitude of charge hence quantization can be neglected.