Marriage Information

Now I need some help with Información matrimonial. I found a record in FamilySearch for Placido Xavier and Maria Antonia Bernardina De Los Reyes with a marriage date of 4 May 1757 in El Sagragrio. I have looked at all of the records for the month of May 1757 and I cannot see anything.

I will admit that I am a little confused by the different types of documents that I am seeing, so I am asking for help. I have looked at pages 178 - 239. I had the same problem with baptismal certificates until someone explained them, so now I need help with marriages.