What defines a series in InfluxDB?

[amberfan]

well, the document of InfluxDB says "a series is a collection of points that share a measurement, tag set, and field key", InfluxDB document, The datas below consist of eight series (the document says):

Series number Measurement Tag set Field key
series 1 census location = 1,scientist = langstroth butterflies
series 2 census location = 2,scientist = langstroth butterflies
series 3 census location = 1,scientist = perpetua butterflies
series 4 census location = 2,scientist = perpetua butterflies
series 5 census location = 1,scientist = langstroth honeybees
series 6 census location = 2,scientist = langstroth honeybees
series 7 census location = 1,scientist = perpetua honeybees
series 8 census location = 2,scientist = perpetua honeybees

but when I execute "show series from census;", there are only four series.

> show series from census;
key
---
census,location=1,scientist="langstroth"
census,location=1,scientist="perpetua"
census,location=2,scientist="langstroth"
census,location=2,scientist="perpetua"

> SHOW SERIES CARDINALITY from census;
name: census
count
-----
4

Why there are only four series ,not eight?