What do the "+n" values mean at the end of a method name in a stack trace?

I believe they're offsets into the code of the method - whether IL or JIT-compiled-assembly bytes, I'm not sure...

(Basically they're taking the place of line numbers, which of course aren't available without the pdbs.)

It means:

it’s an offset into the native instructions for the method.

Read this for more details.

it is the byte offset into native code.

With ILDASM you know why.