im using 5ghz only and i turned off the 2.4ghz channel why on my router shows that thers is 2 signal is connected from the extender but only one device ?

for exaple : on my router app it show that there is one device ( the re650 ) is connected, but actually on the the router screen shows 2 devices, and that's happen only when i connect the extender and there is no problem with the router as the huawei support told me after i asked them.