I don't think it can be done adjusting the Document Footnote Options. But you could right click on the text frame and Text Frame Options>Inset Spacing>Bottom and adjust there.
Thank you so much. You are a star Ellis. It worked.
At the end, when you have finished your work, klick twice on the lower centered end of the last frame as it will optimize the frame's size or apply an Object Style on the last frame which will grow vertically with the amount of text.