If r is the compound interest rate then 7 years is 7*4=28 quarters and after 7 years the accumulated amount is 4000(1+r)^28. Assuming nominal APR (US) is the same as the simple annual interest rate then the quarterly rate r=6.2/400=1.55% per quarter or 0.0155 as a decimal. So on this basis, the accumulated amount is $6153.16.
If the APR is calculated to include compound interest over 12 months, then (1+r)^4=106.2%=1.062 and r=0.01515 approx, so the accumulated amount is 4000(1+0.1515)^28=$6094.41.