Don't understand the meaning of Item.length


I just started learning yjs and I don’t understand how the nodes are related.

const doc1 = new Y.Doc()
let a = doc1.getArray('myarray')
a.insert(0, ['ab','c'])
a.insert(1, ['d'])

I understand it is a linked list structure, but I don’t know what length means.

I learned from the code that the next clock is equal to the previous clock+length

clients = {
     1: [Item({client: .., clock: 0}, deleted = true), Item({client: .., clock: 1, length: 2}), Item({client: .., clock: 3})]
     2: [Item({client: .., clock: 0}), GC({client: .., clock: 1}, length=4)]

What is the function of this length attribute?

Thank you!