'a few' is fairly neutral to expectations and more speaks to the absolute number - of which 4 is 'a few'. If the author wanted to emphasize that this was fewer

'a few' is fairly neutral to expectations and more speaks to the absolute number - of which 4 is 'a few'. If the author wanted to emphasize that this was fewer than expected, 'only a few' would have been appropriate - but this might not have been their intent.