LibreOffice 7.1 Export png/jpg only valid for first (left) sheet?

If my document is a single sheet and if i try to export a sheet in png or jpg, fine. If the document gets two sheets, i cannot manage to export the 2nd sheet in jpg or png. Other said, the export, per default will only consider the first (id:0) left sheet. Is it normal?

With the second sheet being the active sheet, in the export dialog activate the Selection checkbox. Same for a selected cell range.

God-damn, stupid i am. I didn’t see this box. Many thanks!
(i created a macro for exporting selection of cells in a png. Just adding this in the code made the trick, based on the solution above:

dim propFich(1) As New
    propFich(0).Name = "FilterName"
    propFich(0).Value = "calc_png_Export"
    propFich(1).Name = "SelectionOnly"
    propFich(1).Value = TRUE
    adresseDoc = convertToURL(imagefilepath) ' place here a valid path
    thiscomponent.storeToURL(adresseDoc, propFich())