Usually, this would mean to ch 11, sl st join (on the right side) into the 16th st from the fold (this is the center of your sole). --You haven't said if you had to finish off the sole or if this is a continuation. I'm assuming that you did a sl st into the first st of the row??? And, then, the CH-3 starts the first row of the SIDE???-- But, you will be using only the back loop for your sc sts. This puts a nice little 'edge' between the sole and the side of the bootie.
Try this and see if this makes sense with the rest of your pattern. If not, feel free to ask again.
My name is Beverly and I'll be the new crochet editor. I'm still doing 'training for the job' but I'll get back here as soon as I can and I'll have a different name. :)