The position of the target is determined by totwo indicators:
The two indicators are: ELEVATED STOP and MAGICIANS UNCLE.
The number of letters in the word before the second indicator equals the distance (in word pairs) from the first indicator.
So in the first message we have ALARM before the second indicator, which means the distance from STOP to the target is 5
Same goes for the second message with distance 8
In the third message, STOP is not at the end of the message, so there are two word pairs, which have a distance of 3 (word before MAGICIANS is ICE)