Let's say that the settlement is newly founded and that it is in a natural harbour, with a river nearby and access to good commerce (land and sea), although that would most likely be in the (near) future.
How fast could the settlement grow into a town of say 5.000 people or into a city of 20.000-30.000 or possibly more?
And how fast could a settlement that is inland, but at the intersection of travel and trade routes grow to the same figures as the seaside settlement?
Given the economy and societies that persisted in much of Europe in the Middle Ages, population growth has always been much lower than we consider. First off, in order to allow demographic expansion a staple supply of food has always been paramount, paired with a low occurrence of diseases. Most cultures in Western Europe did not practice much in terms of birth control (save from abstinence during Lent or pregnancies) and this favored several children per each family (estimates go from 3 to 6 for most non aristocratic families), especially in regions of labor-intensive farming practices. Secondly, a market wide enough to absorb a diversification of production ad thus a greater number of specialized jobs would concur to this increase in population as parents could foresee future employment.
However all pre-Contemporary societies had low growth rates due to a high infant mortality, to the point of never having more children born in a year than those who had died in the same year. To give you an example, Europe recovered the Black Plague losses of 1347-1350 in the 1600s.
To sum it up, to reach 10000 people from 5000, my educated guess is about 60-70 years without major pandemics and famines