I guess, you have a block like this and you are making a stacked column chart with Value 2 and Calculated Value.
| Value 1 | Value 2 | Calculated Value | |
| Label 1 | 20 | 15 | 5 |
| Label 2 | 25 | 17 | 8 |
| Label 3 | 25 | 28 | -3 |
| Label 4 | 10 | 8 | 2 |
| Label 5 | 5 | 4 | 1 |
What you can do is to have another calculated column as =IF( Value 1 < Value 2, 0, Value 1 - Value 2 ) and use that along with Value 2 in the stacked column chart. That will give you a chart like this:
