That's about the size of it

Hallo,

This is my first post to this forum.I find this forum very inteesting.

What does this phrase "that's about the size of it" mean. I heard it sometime during my stay in England

Thanks

This reminds me of the Sesame Street song, which says, in part...

Oh everything comes in its own special size
I guess it can be measured by where you put your eyes
It looks big when you're close
And it looks smaller back a bit
That's about the size of it...

That's about the size
It's where you put your eyes
That's about the size of it.