nRF Connect Android - what do the arrows mean?

Question

(there isn't an option for nRF Android or Mobile when creating a case!) 
 
 Next to each Characteristic is one or more little arrow icons: 
 
 Where is the documentation which describes what these actually mean?

Musa · Answer

Single arrow means read the current value, triple arrows enables notifications, so when the characteristic value changes, you will see it change on your screen. Data is typically written in hex.