I'm not sure if this is the 'best' way, but 'a' way would be to create a mapping like this:
noremap <Leader>a ^/\d\+<CR>n<C-a>
^ to go to the start of the line
/\d+<CR> to search for the first number
n to go to the next (second) match
<C-a> to increment the number under the cursor, which should be the second number now.
Or perhaps a slightly better way is to use a script
execute "normal \<C-a>"
noremap <Leader>a :call IncSecond()<CR>
search() doesn't set the
/ register and doesn't start highlighting if you have
You could cram those lines in a keybind without a function:
noremap <Leader>a ^<Bar>:call search('\d\+')<Bar>:call search('\d\+')<Bar>:execute "normal \<C-a>"<CR>
But I would go for the readability of the function...