When I purchase shares for my mutual funds, the actual number of shares is always rounded to the nearest 1/1000 (such as 12.345 shares). If FM has a price already (because I've downloaded the prices before I enter the purchase transaction), it calculates the number of shares out to 6 decimal places. This gives an incorrect match with my actual balance in my account.
The Display setting for Share Digits doesn't affect this, as it affects only the display, not the internally recorded value. I have to re-enter the number of shares, at which point the price is recalculated with more decimals to give a precise match for the dollar value of the transaction.
I would like to be able to force all transactions to show a maximum of 3 digits of precision for the number of shares. I would be OK with this choice being either by investment (so that I could make it require whole numbers for regular shares that I purchase) or one setting for the entire application. When a transaction is entered, the price would be automatically adjusted to allow the shares to stay with three decimals. So if the value of the investment is 250, and FM already knows the price is 22.05, rather than calculating 11.337868 shares, it will calculate 11.338, and reset the price to 22.049744 (which is what you get if you enter 250 value and 11.338 shares).
I think I've discussed this before, but I think I didn't have the latest edition of the software, and you suggested a setting I didn't have, so I couldn't see if that would work for me. But I recently upgraded again (I've been a user for over a decade), and I don't see anything that will allow me to set FM up the way I want.