interest of government stock

Dear Tutor, here is a qustion needed to be explained.
During the tax year 2014/15 Bayle will receive interest of £3600 from government stocks (gilts), this is the actual cash amounts that will be received.
my queston is that why they didn’t gross up by £3600×100/80. they instead use £3600 directly and plus brackets like this £ 3600 (gross), may i understant it in this may that any interest on government stock must be treated as gross amount although saying this is the actual cash amounts that will be received.
many thanks