Height is the trick. The marks crossing a stitch’s post say how tall it is — none for half double, one for double, two for treble, one more for every extra yarn over. Single crochet is the odd one out: just an X. Read rounds from the center outward, rows from the bottom up.
* Crochet Bobble’s own symbol. Where a standard defines one we follow it — the Craft Yarn Council first, then the Japanese chart standard. For these stitches neither does, so we drew them and say so: Beginning Cluster (ch 3 + 1 dc together), Beginning Cluster (ch 3 + 2 dc together), Beginning Cluster (ch 3 + 4 dc together), Beginning Cluster (ch 4 + 1 tr together), Bullion Stitch, Linked Double Crochet, Linked Treble Crochet. Check the key of any pattern you meet them in.