Motion Detector Time Adjustment
"I don't really get it why it's 10±5 and not in example 5s-10min." 


Because they they are telling you that the minimum could be anywhere between 5 s and 15 s. They can't guarantee that you can get down to 5 s so they wouldn't specify it like that. 
They designer probably aimed for 10 s and guarantee that it will be 10 ± 5 s. 



Note that there should be a space between the digits and units as per SI standard. We don't write "53bananas" but rather "53 bananas". It's the same with volts, amps, seconds, etc.