add on subdomain too long

[affireve]

I am a new user trying to add on a subdomain to my domain but message comes up it needs to be less than 25 characters.. Is it ok to shorten my subdomain just for the sake of adding it on to the host domain ?

[thewebhosting]

You can not add a sub-domain name having more than 25 characters. Please try to add after making it bit shorter.