What happens if I reported non-taxable reimbursed expenses on my T777?

I reported Entertainment, Travel & Meal Expenses that my employer reimbursed me for in excess of $6000 in 2017. The CRA is now requesting me to provide proof of these expenses and proof my vehicle expenses (log book & car expense costs). Now what will happen in this case? I realize i wasn supposed to claim it as it isnt taxanle (the reimbursed travel costs), so can i just call and admit my mistake and submit the rest? Will the CRA deny all my T777 claims, or will they just re-adjust my return and make me repay the amount oweing for the travel expenses? I also overstated my insurance deductions, but I understated my vehicle maintenance expenses.