to generate a series of hearts in the von neumann ordinal form* equivalent to any given (non-negative) number, just put that number in the first text box (the one for numbers, labelled "number") and click "number → hearts" (or press enter while in the text box)
to do the reverse (as in, generate the original number from the sequence of hearts), put the hearts in the second text box (the one for text, labelled "hearts") and click "number ← hearts" (or press enter again)
to be confused as to what these actually are, be basically anyone :D
*yes, that is what they're called D: (well, something along those lines)