So iI read everywhere, that the 5 GHz frequency (in the EU) can have 19 channels without overlapping. The The 5 GHz frequency goes in the EU from 5.150 to 5.725 GHz, so total 575 MHz. The widewidth of one channel is 20 MHz. 575 MHz / 20 MHz = 28,75 ~ 28 Channel.
I also don't get, where this site has this channel partition: https://www.welotec.com/files/CMS%20Landingpages/5ghz-kanalverteilung-80211ah-1.jpg
(From 5,150 GHz to 5,350 GHz with 20 MHz channel-wide, i'll get 10 channels + From 5,470 GHz to 5,725 GHz with 20 MHz channel-wide, i'll get 12 channels)
For 19 channels, each channel should have a channel-wide of ~ 30,25 MHz (575 MHz / 19 channel)
Edit: Ok i see we have unused channels between channel 65 - 99 (5320 - 5500 MHz). Why are these unused?