Even if the census was alerted in favour of Poles (which I doubt as there is no evidence to support that claim)it couldn't have been alerted too much.Lets go to the extreme and assume for the sake of the discussion that it was 10%. Still it gives 50% of Poles in the Wilno area.
Vilnius city had majority of jews (>50%) before ww1, however surrounding lands (80% of population lived NOT in cities) had more lithuanians than poles. After Zeligowski afair, number of lithuanians started to diminish due to oppression, polonisation, colonization, mass migration and other factors. No wonder lithuanians contituted minority at the start of ww2.
in Kovno that do not bother with numbers or percentages
That area had strong lithuanian majority, so wonder there.