The 5.3M number is not adults receiving RSA, just some number the newspaper made of thin air as an estimate of the total people who may be benefiting from RSA.

The actual number is 2.53M families receiving RSA, with no soecific details on how many people by family (from the agency POV, the number of people actually doesn't matter much. They are taxed as an entity and receive RSA under the same conditions)