"Just how big is the Andromeda galaxy?" (astronomy.com)

http://astronomy.com/news/magazine/2018/02/adromeda-is-the-same-size-as-the-milky-way

If the mass of this very nearby galaxy is already difficult to
measure, does this mean that the total baryonic mass in the
universe is in fact also known only with, say, a factor 2 of
experimental error?

[And could this total error be in the other direction, thereby
reducing the amount of required dark matter?]

--
Jos