employment benefit

can you help in question 100 in kaplan exam kit
During the period from 1 August 2022 to 5 April 2023, Zune plc provided Poppy with a
diesel car which has a list price of £21,800. The car cost Zune plc £20,600, and it has
an official CO 2 emission rate of 75 grams per kilometre. The car does not meet the real
driving emissions 2 (RDE2) standard. Poppy was not provided with any fuel for private
use.
3 Throughout the tax year 2022/23, Zune plc provided Poppy with two mobile
telephones. The telephones had each cost £480 when purchased by the company in
March 2022.
4 All of the taxable benefits provided by Zune plc to Poppy are payrolled.

answer

Car benefit (21,800 × (20% + 4%) × 8/12) 3,488
Mobile telephone (480 × 20%) 96

the question is why he multiply the phone benefit by 20% ?