Simplify the following text for a Grade 5 native English-speaking person.
Original: The original intention was to number the locomotives 958 to 960 , following on from the steam locomotives of the Z class , but as delivered they were numbered 1 to 3 in a separate list from the SR 's steam locomotives .
Simplified: They were numbered 1 to 3 in a separate list from the SR 's steam locomotives .