How the Rectangular canvas works: foundation chain and rows
The Rectangular canvas is a grid: a foundation chain along the bottom, and your rows above it.
A new chart on the Rectangular canvas starts with a foundation chain along the bottom. The foundation is not a numbered row. Row 1 is the first row above it.
Rows are worked back and forth, the way you crochet them. Row 1 opens at the right end, over the last chain of the foundation. Row 2 opens at the left, row 3 at the right again, and so on, turning at the end of every row.
Each row opens with its own starting chain, set by the stitch the row is worked in. Chain One draws it for you, so you never place a turning chain by hand.
You can change or delete the foundation chain if your piece starts differently. Add rows and columns to make the chart as big as your piece.