The timeout value is per try so setting a +time=5 would result in a 15 seconds delay as the default for +tries is 3. If you set +tries=1 then your command will timeout in 5 seconds e.g.
time dig +time=5 @hii.com hello.me
; <<>> DiG 9.3.6-P1-RedHat-9.3.6-16.P1.el5_7.1 <<>> +time=5 @hii.com hello.me
; (1 server found)
;; global options: printcmd
;; connection timed out; no servers could be reached
real 0m15.017s
user 0m0.003s
sys 0m0.011s
or with a tries=1
time dig +time=5 +tries=1 @hii.com hello.me
; <<>> DiG 9.3.6-P1-RedHat-9.3.6-16.P1.el5_7.1 <<>> +time=5 +tries=1 @hii.com hello.me
; (1 server found)
;; global options: printcmd
;; connection timed out; no servers could be reached
real 0m5.015s
user 0m0.006s
sys 0m0.007s