The phrase "a queue of six" is correct and usable in written English.
It can be used to describe a line or sequence of six items or people waiting for something, such as service or attention.
Example: "At the coffee shop, there was a queue of six waiting for their morning caffeine fix."
Alternatives: "a line of six" or "a row of six".
"I auditioned yesterday in a queue of five others.
By mid-morning on a Monday, the exhibit was crowded, and a queue of thirty or so people had formed at the entrance.
Monkey hears there is a queue of eight for the three vacant slots with a grand selection committee making the final decision next Wednesday.
On the turquoise horizon a queue of eight tankers waits to be filled by the output of the world's second-largest iron-ore mining operation.
The idea hit the headlines again this week, and the publicity has created a queue of seven corpses waiting for the world's first promatorium to open next year in the Swedish town of Jonkoping.
Within minutes of a tanker's arrival, a queue of a hundred, and the driver calling armed police, because he cannot part with all his minimal supplies here.
There's usually a queue of about ten people in the toilets whilst you're trying to make yourself look half decent, you usually end up rushing on stage with one shoe on or something.
It's a classic setting for things like film junkets, where a queue of journalists get five minutes to ask famous people the same two questions.
At the busiest crossings, cars face a queue of up to four hours.
"Long queues at petrol stations have returned to this relatively peaceful enclave, Fazel writes: A taxi driver in a queue of a few hundred taxis on Kasnazan road in East of Irbil says the word on the street is the petrol in Kurdistan region which is locally produced is being smuggled into Mosul and other areas where there is a shortage because of the fightings.
