General number field sieve function

Question

I have some questions about the General number field sieve - function on which I can't find an answer on the internet.

In general:

The GNFS-function $f(n)$ with $n$ the number for which we search the factorisation shows the complexity of that factorisation:

The GNFS-function gives the next aproxiations for the strength of RSA-moduli:

Questions:

1. $n$ is the number for which we search the factorisation, but is this number a number in base 10 or in bits? Because the table gives values in bits?
2. What is the meaning of the $o(1)$?
3. How much digits has an RSA-modulus of size 1024 in base 10?

Thanks for the help!