It usually is bigger, and comes with a certain lock. What is it?

Question

What is this poem about?

I only have it once
most of you do too

It's easy to imagine
how I could have a few

It usually is bigger
and comes with a certain lock

But it's smaller by 40
from a small one in the flock

Hints

1.

in 'It's easy to imagine / how I could have a few', I would count either 18 or 34

2.

Mind the semantics. The poem describes something, but it's not in first person, i.e. 'I' in the poem doesn't refer to the answer. Then What does it refer to?

3.

Smaller by 40, not from any "small one" but from a closely related one.

4.

I have exactly Two

5.

I is context dependent. It refers to the same type of thing each time, but not the same specific thing. (By the way I have four)

And I have two

Answer 1

Reconsidering a possible answer is

Capital letters

I only have it once most of you do too

Refers to the line pair itself with 'I' being the only capital. This interpretation fits with Hints 4 & 5.

It's easy to imagine how I could have a few

This line currently has only 2 capitals - but see Hint 1 for how this may be increased.

It usually is bigger and comes with a certain lock

Capitals are usually larger (b, d, h, k, l, same height) and may be applied by the Caps Lock key.

But it's smaller by 40 from a small one in the flock

In Ascii Octal capital letters 'A' = 101, 'a' = 141 ... and so on to 'Z' = 132, 'z' = 172.
_{The capital letter in Octal! is 40 smaller than the small one.}

Hint 1. in 'It's easy to imagine / how I could have a few', I would count either 18 or 34

Writing this line in full without the apostrophe: It is easy to imagine how I could have a few.

This has 34 total letters and 18 different letters as repeated are: 5i, 2t, 2s, 4e, 4a, 3o, 2h, 2w.

Hint 2. Mind the semantics. The poem describes something, but it's not in first person, i.e. 'I' in the poem doesn't refer to the answer. Then What does it refer to?

'I' is the stanza line itself.

Hint 3. Smaller by 40, not from any "small one" but from a closely related one.

Capital letters are 40 less than in value than their corresponding small letter in Ascii Octal!

Hint 4.

I have exactly Two

'I' and 'T'

Hint 5.

I is context dependent. It refers to the same type of thing each time, but not the same specific thing. (By the way I have four)

And I have two

'I', 'I', 'B' and 'I' → 4

And I have two: 'A' and 'I' → 2

Answer 2

I only have it once most of you do too

I have one Home Key and also one real Home most of you also have one home

It's easy to imagine how I could have a few

It is easy to imagine having multiple Home, House

It usually is bigger and comes with a certain lock

Real Home is usually big not as small as a key in keyboard and it has certainly a lock

But it's smaller by 40 from a small one in the flock

The Home key code is 36 smaller than other keys l is 76 the last letter in Home Row and in the word small

The Answer

Home (House)

Answer 3

I can't really back my answer up but, Is it just simply a

key?

I only have it once most of you do too

As in a house key

It's easy to imagine how I could have a few

Either multiple keys on a keyboard, or a reserve (house) key

It usually is bigger and comes with a certain lock

This could be either a house, way bigger than a key(board) and with a door lock. More plausible would be a keyboard, bigger than just one key and it has a caps lock.

But it's smaller by 40 from a small one in the flock

Just one from 40 keys on a keyboard? Though most keyboards have way more

in 'It's easy to imagine / how I could have a few', I would count either 18 or 34

One keystroke compared to all needed to write that sentence, even though I am always one or a few keys off when counting.