taxable benefit

John was employed by Z PLC at a salary of 35,000 a year. He was provided with a computer for private use on 6 November, 2013.The market value of the computer when first provided to an employee for private use was 3,600 and had a market value of 2,000 when provided to john for private use.Z PLC gave the computer to john on 5 April,2015 when it had market value of 1,000.

My question is why have said told us twice in the end that it had a market value of 2000 when provided to john…then again in the end it had a market value of 1000 on April 5 2015…why twice….and how do we get the use I.e 3600×20%=720 .which is added to 2580.thanks