Compensation Element for ESOP

I have received a 1099-B for shares sold as part of an acquisition. These shares were originally bought as part of an ESOP which spun off other companies which spun off other companies. Luckily then have a nifty cost basis calculator  from the company so I know the cost basis. I've entered that. I have checked that it came from an ESOP. It's asking me for a "Amount of Compensation from this sale." What is this and where do I find this?