Thanks for bringing this issue to my attention. It appears that you have hit some behaviour that's reproducible in our Flash 3 charts as well as our Flash 5 charts with APEX 4.0. I believe the reason that it wasn't apparent before now, with the Flash 3 charts, is because there was no option to display a value on the gauge pointer with the earlier charts. With APEX 4.0, we've extended the Chart Attributes to allow for the display of the value. Obviously in your case, the incorrect value is being displayed and will be misleading to your users. I appreciate this is not ideal, but if possible I would suggest updating your attributes to switch off the display of the Value on the gauge. I will address this in a future release, as with the exposure of the "Value" attribute with Flash 5 charts, we don't want to be displaying incorrect information. Thanks again for bringing this to our attention, and hopefully by switching off the Value attribute, you can still proceed with your use of the gauge chart.
To be honest, I cannot give you an exact timeframe right now, so my suggestion would be to revert to a different chart type for the time being. Again, I appreciate this isn't ideal, but we will address this in a future release.