Select icon size
Repeat Icons can be resized to any size and keep their quality. However, when they are inserted into a spreadsheet, they become a picture with a set number of pixels. So if you insert an icon at say 100x100 pixels and then resize you picture within your spreadsheet to 200x200 pixels, then you will loose quality.
You can use this tab to select the required size. If you are not sure, then just insert the icon at 100x100 pixels and then resize within your spreadsheet by clicking on it and using the resizer handles:
When you have sized icon as required, you can double click it to open this screen again and adjust the pixels settings.
Changing an icon's size
If you are editing an existing icon, then you will also see:
the 'Current size on sheet' area and then 'Set to current size' button. Clicking the button will change the icon's number of pixels to match the size you have the icon within the spreadsheet. This gives the best quality image.