A duplicate/off-topic flags requires 10 votes. Why 5 names appear after that question is set to duplicate/off-topic?

@Biswapriyo No they dont. Closing requires 5 votes from a normal user. A single vote from a gold badge holder or a moderator is also binding.

Only 5 users with >2k rep are needed to close. Users below 2k rep can push it into review but their votes don't count towards the close.

@Mokubai When I click the 'flag' option in a question, the popup shows '19 remaining'.

@Biswapriyo that is how many flags remaining that you can cast today...

@Mokubai Ooooo... I misunderstood that. Thanks for clarification ;)