Explanation

Out of 565 princely states during 1947, 13 princely states decided to join Pakistan.

History ;

At the time of Indian Independence, there were a total of 565 states, Small and large combines

After independence, These states were given the option to join any of the two newly formed dominions, India or Pakistan.

Pakistan (West and East) Constituted about 20% of the total area of British India

They managed to get hold of 13 princely states