cue 1 is the first cue you add to your workspace
cue "1" is the cue numbered 1
they may be the same thing, but cue 10 and cue "10" are almost certainly not the same thing.
so in a script, someCueNum needs to be a string and if a number can be converted by using "as string"
this should do what you want
tell application id "com.figure53.QLab.5" to tell front workspace
repeat with cueNum from 104 to 1604 by 100
try
set armed of cue (cueNum as string) to false
end try
end repeat
end tell