ES cluster setup issue on ec2

Too many machines returned. About 98 machines in discovery nodes list.
Most of them don't have ES installed.

I tried to use groups to filter, but it doesn't work.

Here is my setting:
discovery:
type: ec2
ec2:
ping_timeout: 5s
groups: sgn2-stg-sss
any_group: false

I'm sure only 3 machines within the group. What should I do to filter
out?

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