As long as you enter the correct total Sales Price and Cost Basis, the number of shares you report doesn't make any difference. You can enter "100,000" or "1".
If you are concerned about this approach you can also make two more 1099-B entries, each for 100,000 shares sold on the same day with a Sales Price of "$0" and a Cost Basis of "$0".
The IRS is only concerned about the total dollar value of the transaction. The number of shares is entered as a convenience to you - it helps you in keeping track of your entries.