Explanation ::

After cutting links 4 and 11, he would be left with :
(A) Two chains of 1-link length each : link 4 and link 11.
(B) One chain of 3-link length : link 1~3
(C) One chain of 6-link length : link 5~10
(D) One chain of 12-link length : link 12~23

He then pays the 2 chains in (A) for the first 2 days.
On day 3, he gets back the 2 chains and gives (B) chain as rent.
Then pays 2 (A) chains for next two days.
And gets back 2 (A) chains + the (B) chain on day 6 and gives (C) chain as rent.
Then pays the 2 (A) chains and the (B) chain as rent for next 5 days.
And gets back all chains and pays the (D) chain as rent.

Then, he repeats the above steps till day 23.