There is a simple way to obtain the answer you need. Open the software then switch to Easting/Northing. On each section, next to Grid press the Browse button. It's a ...(dots) button. On the bottom of the window, there is a Find section. You can do the same for both sections. Type there UTM ZONE 28 and UTM ZONE 29. Since there are many like these, double click the zones to choose the corresponding country.