Confusion about the ramping-arrival-rate executor

I am following the k6 tutorial on spike testing which uses the ramping-arrival-rate executor to increase the request rate instantaneously.
Here is the test definition

import http from 'k6/http';
import { sleep } from 'k6';

export const options = {
  scenarios: {
    contacts: {
      executor: 'ramping-arrival-rate',
      preAllocatedVUs: 50,
      timeUnit: '1s',
      startRate: 50,
      stages: [
        { target: 200, duration: '30s' }, 
        { target: 500, duration: '0' }, 
        { target: 500, duration: '10s' }, 
      ],
    },
  },
};

export default function () {
  http.get('https://test.k6.io');
  sleep(1);
}

My expectation is that the request rate ramps up from 50 to 200 req/s over 30s and then jumps to 500 req/s where it stays for 10 seconds.

To validate it I upload the metrics to datadog and visualize it on the k6 dashboard that comes out of the box on datadog. I take the k6 output json, filter on the objects where metric = http_reqs, then bin the timestamp of those objects in 1 second intervals. The resulting counts per 1 second interval are then uploaded as a datadog datapoints (via http api).

Now, the confusing part is the requests rate chart looks like it’s sending consistently about 50 requests per second. Does this look right to you? I would have expected an increase from 50 to 200 over 10s and then to 500 requests per second as set out in my test script.

Thanks

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