Extra Decimals After Fund-to-ETF Conversion

What I cannot figure out is how the extra decimals are created. I recently did a tax free mutual fund to ETF conversion and after performing a stock for stock transaction in quicken, went through line by line to edit the number of shares (adjusting the average price) in order to match the broker, which is exactly 4 decimal places. I have tracked this separately in Excel and confirmed that the four decimal lots shares add up to a number that is exactly 4 decimals (i.e. if there were a 5th decimal, it would be "0"). However, Quicken maintains these extra decimals that don't come from the addition of the individual lots in total…perplexing