The pattern is written in US terms.
You may want to make the pillowcase 0.5 inches smaller than the actual pillow insert. To make sure that your pillowcase fits perfectly without any loose areas, pumps or gaps.
You can adjust the length of the pillow by adding or subtracting rows from the right and left.
Your stitch count throughout the whole pattern will be 59 stitches. You may watch this tutorial and apply it throughout the pattern to help you achieve straight edges
I will be referring to the cream color with color a & to the beige with color b
If you are following the written pattern you may need to take a look at the chart every now and then to make sure you are on the right track