Statement of Cash flows. "Test your understanding 1 of the Kaplan text"

Hello! I am having an issue with the answer of TUI 1 of chapter 19 in the Kaplan study text. My query is this. Why in the book the contra between payables and receivables of 230 is subtracted twice from the trade receivables balance? (1st as recognition of earlier ommision and then from the balance c/f) Is it not double counting? I am posting a question here for the first time, I hope my query will be answered soon. Thank you. Pasting question and its solution here. Q: The following information relates to Flute, an entity. Statement of financial position for the year ended 30 September – extracts 20X8 20X7 $ $ Trade receivables 31,250 35,633 Trade payables 14,195 13,750 Accrued wages expense 1,015 835 Interest payable 350 300 Income tax payable 1,250 1,075 ––––––– ––––––– Statement of profit or loss for the year ended 30 September 20X8 – extracts 20X8 $ Sales 427,915 Purchases 165,000 Wages 52,750 Interest expense 325 Income tax charge 1,515 ––––––– Note: At 30 September 20X8, Flute had agreed to, but not yet accounted for, a contra between trade receivables and trade payables amounting to $230. Excerpt of the solution worrying me: Receivables’ ledger control account $ $ Balance b/f 35,633 Cash receipts (ß) 432,298 Contra with payables 230 Sales revenue 427,915 Balance c/f ( 31,250 – 230) 31,020 ––––––– ––––––– 463,548 463,548