Purpose of duplicate contact in series on a single rung

I have pulled the Ladder listing from the GE 90/30 without any other documentation.
Viewing the ladder print out, I see several instances where the same contact is used in series with no vertical wires between.

I have this rung (actually rung 48 in a MANUAL Block)

-]1[------]2[----]3[---]4[----]5[---]4[-----------------------<+>
<+>------]6[----]7[---]8[--------]etc[------------------------------( )

All the contacts are NO, with contact 4, an %I0006 (vacuum sense bellows), used twice in series on this one rung.

Is this for a purpose? Redundancy? Or legacy of some earlier edit?

Inquiring minds....

TIA

Cal

Hi
Earlier GE 90-30 low end CPU's did not allow online edits but you could overtype the instruction so some people (me included) would adopt a double contact to either reserve a contact or to remove a contact...
Although I would use %S7 Always on

I think cjd1965 has the correct explanation. The CPU311 does not allow editing a rung without stopping the PLC, but it does allow you to replace one address with another while running. Probably someone monitoring the rung during startup realized he didn't want what was originally programmed at one of the instances of %I0006 and replaced it with a second instance of %I0006. His intent would probably have been clearer if he had replaced the contact he didn't want with %S0007 (ALW_ON).

Makes sense

Danke!