Casting on question

When casting on, If the directions say "cast on 28 stitches, does the 28 include the slip knot I started with or is it 28 after I have the slip knot on the needle? Thanks for helping a newbie!

Count the slip knot as a stitch and work it, knit or purl it on the next row. Depending on which cast on you use, you could drop it off the end of the needle after you’ve cast on and then, don’t count it as a stitch.
The idea is that you start the next row with 28 loops over the needle.