the text contains a math expression. The math expression can be interpreted as an abstract syntax tree. The AST can also be translated into bytecode and interpreted by a stack-based virtual machine.

The op-codes are where you do that translation from an AST into bytecode. The entire 2nd half of the crafting interpreters book will guide you through how it's done. https://craftinginterpreters.com/a-bytecode-virtual-machine....