Gitlab runner configuration to pick up jobs only at a certain interval

As per the below gitlab-runner config.toml, 1 job should be picked up within an interval of 15 seconds, but everytime when the pipeline runs, it is being over ridden by concurrent parameter, which picks up the number specified in concurrent. Please help with the configuration setup with reference to the below one so that if a pipeline is triggered, it will pick each job at every 15 secs till it reaches the concurrent value.

listen_address = "0.0.0.0:9356" concurrent = 6 check_interval = 15 connection_max_age = "15m0s" shutdown_timeout = 0

[session_server] listen_address = "0.0.0.0:8093" session_timeout = 1800

runners name = "XXXXXXXX" output_limit = 20971520 request_concurrency = 1 url = "https://XXX.com" id = 73379 token = "XXXXXXX" token_obtained_at = 2024-12-09T06:27:56Z token_expires_at = 0001-01-01T00:00:00Z executor = "docker"