## Bug description

We have an issue in which the table of users for each cohort does not contain the same number of users as the table reports.

### Example
([Source](https://app.posthog.com/insights?startEntity=%7B%22actions%22%3A%5B%5D%2C%22events%22%3A%5B%7B%22id%22%3A%22user%20signed%20up%22%2C%22type%22%3A%22events%22%2C%22order%22%3A0%2C%22name%22%3A%22user%20signed%20up%22%7D%5D%2C%22new_entity%22%3A%5B%5D%7D&returningEntity=%7B%22events%22%3A%5B%7B%22id%22%3A%22%24pageview%22%2C%22name%22%3A%22%24pageview%22%2C%22type%22%3A%22events%22%7D%5D%7D&retentionType=retention_first_time&date_to=2020-04-05T12%3A59%3A36.001Z&period=w&display=ActionsTable&properties=%5B%7B%22key%22%3A%22id%22%2C%22value%22%3A71%2C%22type%22%3A%22cohort%22%7D%2C%7B%22key%22%3A%22%24current_url%22%2C%22value%22%3A%22www.posthog.com%22%2C%22operator%22%3A%22not_icontains%22%2C%22type%22%3A%22event%22%7D%2C%7B%22key%22%3A%22%24current_url%22%2C%22value%22%3A%22https%3A%2F%2Fposthog.com%22%2C%22operator%22%3A%22not_icontains%22%2C%22type%22%3A%22event%22%7D%2C%7B%22key%22%3A%22%24current_url%22%2C%22value%22%3A%22localhost%22%2C%22operator%22%3A%22not_icontains%22%2C%22type%22%3A%22event%22%7D%2C%7B%22key%22%3A%22%24current_url%22%2C%22value%22%3A%22127.0.0.1%22%2C%22operator%22%3A%22not_icontains%22%2C%22type%22%3A%22event%22%7D%2C%7B%22key%22%3A%22%24current_url%22%2C%22value%22%3A%220.0.0.1%22%2C%22operator%22%3A%22not_icontains%22%2C%22type%22%3A%22event%22%7D%5D&insight=RETENTION))

**Table shows 6 users in cohort:**
<img width="222" alt="" src="https://user-images.githubusercontent.com/5864173/102359528-867d9500-3f76-11eb-8134-50d0adcbd5b8.png">

**Persons list shows a lot more than 6 users in cohort:**
<img width="150" alt="" src="https://user-images.githubusercontent.com/5864173/102359599-9a28fb80-3f76-11eb-9cb8-61b37ddd4d95.png">


## Expected behavior
The persons list and the retention table should match.


## How to reproduce

See description above.

## Environment

Cloud, Clickhouse.

## Additional context

Currently blocking internal personas analysis.

#### *Thank you* for your bug report – we love squashing them!

posthog/queries/test/test_retention.py
for distinct_id, timestamp in user_and_timestamps:
                event_factory(
                    team=self.team, event="sign up", distinct_id=distinct_id, timestamp=timestamp,
                )
            sign_up_action = action_factory(team=self.team, name="sign up")
            return sign_up_action
        def _date(self, day, hour=5, month=0):
            return datetime(2020, 6 + month, 10 + day, hour, tzinfo=pytz.UTC).isoformat()
        def pluck(self, list_of_dicts, key, child_key=None):
            return [self.pluck(d[key], child_key) if child_key else d[key] for d in list_of_dicts]
    return TestRetention
def _create_action(**kwargs):
    team = kwargs.pop("team")
    name = kwargs.pop("name")
    action = Action.objects.create(team=team, name=name)
    ActionStep.objects.create(action=action, event=name)
    action.calculate_events()
    return action
class TestDjangoRetention(retention_test_factory(Retention, Event.objects.create, Person.objects.create, _create_action)):  
    pass