The ARPS purchases should have no impact whatsoever on the present NAV because that is the common value once all of the ARPS are subtracted at par today. The only impact will be reduced volatility in the future. NAV if no prive changes will stay at 8.35
My understanding is that to calculate the NAV required to meet the 200% coverage in order to permit the fund to pay the dividend one must divide the ARPS amount by the number of shares outstanding.
Assuming this is correct, reducing the ARPS by the amount of the buyback does affect the NAV required in order to pay a dividend. It does not affect the actual NAV (which I assume is what you are meaning).