(すうだい)

すうだい
noun
several (vehicles or machines)
quantity
1. several vehicles or machines; a few units
An unspecified small number — usually a few to several — of things counted with the counter (だい) (cars, machines, appliances). The prefix (すう) attaches to a counter to mean "several."
(くるま)数台(すうだい)()まっている
Several cars are parked.
Several computers were lined up at the venue.
工事(こうじ)ため道路(どうろ)重機(じゅうき)数台(すうだい)(はい)っている
Several pieces of heavy machinery are on the road for the construction work.

The prefix (すう) attaches to a counter to mean "several" or "a few" (typically two to eight or so). With (だい), the counter for vehicles and machines, 数台(すうだい) means several cars, computers, appliances, and the like.

THE (すう)〜 PATTERN:

Use 数台(すうだい) only for things counted with (だい); switch the counter to match other kinds of objects.