Welcome to posting!
I find myself wondering if your question might be what the abbreviations mean. :shrug: This is a crochet pattern and you have joined a knitting help forum. I’d like to know if English is your first language. US to UK crochet term differ, so that could be part of your question.
[B]Ch[/B] is a chain stitch.
[B]Sc[/B] is the US English single crochet (UK English use the term DC or double crochet)
[B]sts[/B] is an abbreviation of stitches, and they are giving a stitch count at the end of each round ®.
[B]BPsc[/B] is a back post single crochet. :think: (This is usually done with double crochet - US or Treble crochet -UK stitches or larger).
This is a three dimensional pattern, not only are you crocheting around in a circle but it will not lay flat. R4 will begin to give it a cup or bowl shape.
One odd detail is that the pattern does not say to join at the end of a round with a slip stitch and then a chain to raise your hook up to the top of the next round. This could mean the author intends you to make a spiral and not separate rounds. If it is a spiral, you would be well advised to use a scrap of contrasting color yarn to mark the end of your first round. *Amigurumi is done in this method.
In any case it should look like you are crocheting a skull cap or beanie hat for an egg.
Post again to let us know if we have helped you or if you have more questions about specific instructions.
That back post single crochet, perhaps? I’ll look for a drawing or video to link.
Learning to read crochet patterns: ([B][U]Annie’s Attic[/U][/B])
( http://www.anniesattic.com/crochet/learntoread.html )
Amigurumi video: (Wonder How to)
( http://www.wonderhowto.com/how-to/video/how-to-crochet-japanese-amigurumi-dolls-using-single-crochet-222609/ )