a repeater doesn't increment

[Jude DaShiell <jdashiel@panix.com>]

I am likely doing this wrong but will describe what has been done.
I put an agenda time stamp into a field in test.org and add +4w to the end
of the time stamp inside the >.
I get on the left of the field column on the vertical character and type
control-space to set mark.
I move to the end of the field on the > sign and type space and another
vertical to close the column entry for that field.
Next I do control-c+x+v and am told strings are copied to the kill ring.
Next I move down one line and type control-y to yank those strings out of
the kill buffer and paste them on that line.
When this is done, I expected the time stamp to increment by 4 weeks.
What happened was the same information got copied down and it didn't
increment.
What am I doing wrong?