"des" doesn't mean "some".
"des" is an indefinite article for plural nouns which doesn't exist in English.
So basically :
"Il vend des voitures" = "He sells cars"
However, in English "some" can have a function of emphasis instead of defining the quantity, so it can be used when there is no defined quantity.
Like so :
"Il vend des voitures." = "He sells some cars"
Finally, when "some" is used for quantity purposes, it can be translated as "quelques" or "un peu de", depending if the noun is a countable object or an uncountable object.
It would be subtle in this example, because the "d" sound at the end of "vendent" would run into the "d" sound at the beginning of "des". I believe an experienced ear would still catch it, because there would be a slight lingering on the "d" sound. Actual Francophones feel free to correct me here.