The same person compiled the Lutheran marriage indexes for Bischwiller, 1684-1745 and 1746-1787. Your page is from the 1746-1787 volume, as noted in the text at the top of the page. Each page of 1746-1787 has a "fol" (folio) and number at the top. A folio is a single sheet, consisting of front and back sides. In this case, on folio 52 (front) you will find the marriage, 4 Dec 1780, of MANNHARDT Johann Heinrich, brick-maker from Fuhlbach, Wuerttemberg, to BROHMANN Anna Maria, dau of Johann Georg Brohmann, citizen and shoemaker here in Bischwiller. Johann Georg Bromann, brother of the bride, also signs. The marriages are individually numbered in the book, and this one is #242, but the marriage numbers weren't used for the index.
This is image 54/78 of the book M 1746-1787. Easy to spot, since the names are written out in the margin.
NB, there is also a book M 1684-1745, which likewise has an index, compiled by the same person who did the 1746-1787 (Pastor Roederer, I believe). In the 1684-1745 index, the references are not folios but the individual marriage #s assigned in chronological order. I don't see Brohmann, or any "misspelling" for it that I can think of, in the 1684-1745 index.