movingSum(31day) does not return result

Hi

I use this data :
david.metricA 3 1550240100
david.metricA 6 1550241000
david.metricA 2 1550241900
david.metricA 4 1550242800
david.metricA 50 1550243700
david.metricA 3 1550244600
david.metricA 1 1550246400
david.metricA 3 1550247300
david.metricA 2 1550248200
david.metricA 2 1550249100
david.metricA 1 1550250000
david.metricA 1 1550250900
david.metricA 1 1550252700
david.metricA 5 1550493000
david.metricA 4 1550493900
david.metricA 3 1550495700
david.metricA 1 1550496600
david.metricA 5 1550501100
david.metricA 3 1550509200
david.metricA 4 1550583000
david.metricA 4 1550674800
david.metricA 1 1550741400
david.metricA 2 1550742300
david.metricA 3 1550745000
david.metricA 3 1550745900
david.metricA 1 1550747700
david.metricA 3 1550748600
david.metricA 2 1550752200
david.metricA 1 1550758500
david.metricA 2 1550763000

I don’t unterstand why moveSum does not return for this query :
movingSum(david.metricA,“30day”) (grafana time range : all ranges)
or
movingSum(david.metricA,“7day”) (grafana time range : form -30d until now)

But these queries work :
movingSum(david.metricA,“7day”) (grafana time range : form -7d until now)
movingSum(david.metricA,“23day”) (grafana time range : form -7d until now)

I did many tests, but do not understand why somes queries do not return result (all values are null)

Thanks for your help.

David.