This problem has now been resolved in the new version released today. A number will now only be displayed at the top of the grid for the overall profit available from greening, if it can be achieved. So it will not display a value if some of the runners have no available prices to green against, for example if a goal has been scored after you backed the 0-0 correct score market, or a horse that you backed falls over and its price goes to 1000.
For full details of the new version, please see the version history section of the forum.
Thanks again for bringing the issue to my attention. Kind regards,
Gavin