employee stock option vesting rounding error

unknown

I have entered a stock option grant and it is mostly tracking fine.  But I have passed the first one year cliff and now I vest about N shares each month.  I say "about" because it is not exact and some months I vest N-1 shares.  My problem is that Quicken chose which months to make N-1 and it chose differently than my employer did.  How can I adjust this.  The total number of shares is right, but some months I actually vest N shares and I do a same day sale of N shares, and then Quicken won't let me enter the transaction because it thinks I really only have N-1 available to vest.