Cell types in Microsoft Excel are generally set on the formatting menu. In JCVGantt Pro, you can right click on any cell and select Cell type...

Note that JCVGantt Pro often assumes that the result of an operation is a "String" of text which sometimes causes cells where you'd expect the result of a formula show a blank cell. This is often simply a type conversion issue, and the solution is to change the cell type.

Try experimenting with this to see the results.

Once you select Cell type... you'll see a list of 4 cell types. You can select any of the four types as is most appropriate to the cell you're using.;