Signature on a charter?

I returned to my voluntary job, cataloguing the Laing Charters at the University Library this afternoon. Here's a signature on the back of Charter 2540 which caught my attention - it's my husband's (Sunday) name! I wonder if this was written by one of his ancestors?

On a more realistic note, the style of handwriting doesn't look very sixteenth century to me and I think it was written by another person keeping track of these charters, perhaps in the nineteenth century? However, John Forrest gets a mention in the manuscript itself, so that's definitely of interest.