I seem to have a knack for finding patterns with instructions I can't figure
out.

This one is the Aran Style Jacket from the 2002 issue of Knit-It (picture on
pg 69, instructions on pg 105).

There is a 16 row repeat creating a lattice pattern, and in there, are
instructions to "Sl1p" and "Sl2p" -- which would on first glance seem to be
just slip 1 purlwise and slip 2 purlwise. But there are instructions under
"special abbreviations" which make it sound different, and I *think* it has
something to do with a cross.

The special abbreviations a

Sl1p -- With yarn at back of work, slip next stitch onto LH needle purlwise
to RH needle

Sl2p -- Same as Sl1p, but over two stitches

Used in the context of one of the row instructions: "Knit the knit
stitches, and sl1p each purl stitch"

With the Sl1p, I'm wondering if there is a typo -- when it says "slip next
stitch ONTO LH needle", it makes it sound like you are moving a stitch from
the RH needle tothe LH needle -- so I'm wondering if it should have been
"ON" instead of "ONTO" -- which would make it a regular slip stitch purlwise
(and it would seem like it would be clearer to say "slip each purl stitch"
instead of "sl1p each purl stitch". But then the Sl2p doesn't make sense.

Any ideas?