Why quark charges in multiples of e/3 don't contradict charge quantization

[Rishabh Narula]

"a charge smaller than e has not been found.
if one determines the amount of charge on any charged body like a
charged sphere or charged drop) or any charged particle
(like positron, a-particle)
or any ion, then its charge is always found to be an integral multiple of e,
i.e., e,3e; 4e,...
No Charge will be fractional multiple of e like 0.7e or 2.5e."

the book(notes actually) also gave this side note-
"The existence of charged particles called,quarks
whose electric charges come in multiples of e/3,
would not alter the fact that charge is quantized-
it would merely reduce the size of the basic
unit from e to e/3"

my question is wouldn't that still imply then
that a charge smaller than e does exist since
charge of quarks comes in multiples of e/3.
it would make sense if you add something more
like an isolated quark doesn't exist
like they always come in triplets
or of that sort such that the sum of charges
always adds up to e anyways.am i getting
it right.do correct if wrong.

 

[scottdave]

"a charge smaller than e has not been found.
if one determines the amount of charge on any charged body like a
charged sphere or charged drop) or any charged particle
(like positron, a-particle)
or any ion, then its charge is always found to be an integral multiple of e,
i.e., e,3e; 4e,...
No Charge will be fractional multiple of e like 0.7e or 2.5e."

the book(notes actually) also gave this side note-
"The existence of charged particles called,quarks
whose electric charges come in multiples of e/3,
would not alter the fact that charge is quantized-
it would merely reduce the size of the basic
unit from e to e/3"

my question is wouldn't that still imply then that a charge smaller than e does exist since
charge of quarks comes in multiples of e/3.
it would make sense if you add something more like an isolated quark doesn't exist
like they always come in triplets or of that sort such that the sum of charges
always adds up to e anyways.am i getting it right.do correct if wrong.

I'm not sure which book it is. From what you stated, it appears the author of the book does not know what the charge on a quark is, but is stating that if quarks have a fractional charge, they will still be quantized.
Like you couldn't split a proton and get 1 over sqrt(2) as one of the "pieces".

For "regular" particles, we have only encountered integer multiples of e.

 

[mfb]

All elementary particles have an electric charge that is a multiple of e/3.
All particles (elementary or composite) that can exist freely have an electric charge that is a multiple of e, as quarks always come in combinations that add up to a multiple of e.

 

[mathman]

Proton have 2 up quarks (charges at 2/3e) and one down quark (charge at -1/3e). Neutrons have one up and two down quarks. Mesons have various combinations, such as a quark plus anti-quark of the same kind.