Horizontal Multistage Pump

Hi,

Few days ago I have purchase a multistage horizontal pump. Its motor power is 15 hp. But after purchase I can not justy its stage.

At the pump arrangement there are 8 segments. 6 stage are identify its impeller. But other 2 impeller (stage) are at suction and delivery side. But at the time of puchasing they said that it is 7 stage pump.

So kindly let me know how can I justify it.

Mostafiz