When entering in a Sale (or Listing) you have the option to "Count As" as a full sale, half sale, or do not count. These only reflect in your target NUMBERS, not commission $ or % figure.
So, if you marked the sale as "Half a Sale" it would reflect as 0.5 Sale for the month.
Or if you didn't want to count the sale in your target for the month, but wanted to add your income for the month you could mark the sale as "Do not count this sale" zero.
This allows you to still enter your Commission % correctly and also the Commission $ value as relevant to your share of the sale. Refer to this Help Doc for reference on commission splits.