Why is the query result not within the query period?

There is a query statement whose query period is greater than ‘2024-05-01 00:00:00’.

select time_bucket('1 day'::interval, "time") as recode_time,
from water_meter1
where meter_code = 'metxjjszxnsb1'
  and (time >= '2024-05-01 00:00:00'::timestamp)
group by time_bucket('1 day', "time"), meter_code
order by recode_time, meter_code;

But why is the time of the first record ‘2024-04-30 08:00:00+08’?