I designed this top to be convertible - it can be worn as a corset on the top of a shirt or dress, as a halter top (hence adjustable drawstring), or as a tank top because it has removable straps.
Pattern is not sized to different sizes, only S.
To size for yourself:
measure your bust circumference, make a pattern swatch, count how many stitches you have per one inch, multiply your bust measurement by the number of stitches per one inch, you will get a number of stitches you have to cast on for your measurement. Then divide number of stitches you have per stitches per pattern repeat and you will get a number of pattern repeats you have to make.
Example: bust 36” x 8 stitches (per inch) = 288 stitches to cast on. 288/16 (pattern repeat) = 18 pattern repeats in my 288 stitches. Easy!