If you are confident in the calculation performed and you perform it on the toroidal core, then after clicking APPLY, the Transformer Wizard closes and you will proceed to determining the dimensions of the core and selecting the diameter of the wire wound on the toroid.

If you carried out the calculation of the Physical. character. (enter the cross-sectional area of the core and the effective length of the midline), then pressing this button does not make sense, because further calculation is suitable only for the toroidal core. For other core types (e.g. ELP), you will have to calculate the number of wires and their diameter other way.