Originally, there was only one wire on the large terminal (besides the battery cable); it was 14-ga. brown (fusible link wire) at the terminal, then had a molded-in splice, then became 10-ga. red as it entered the harness. Sounds like a previous owner fried the original fusible link and replaced it with a fuseholder. The second wire you have on the large terminal was probably a direct feed for a stereo.