Just a question here: Should you or shouldn't you make a change? And do you need to see what happens?

Have you tried to understand what the code does? Have you tried to single-step the code with pen and paper and keep track of the values you have in different registers, memory cells and in applicable situations flag register before and after each instruction?

You wonder if there is a print error in the book - the answer to that should be obvious to you. You can't just copy/paste code and pray for the best. Before you copy code, you have to make sure that you understand it. I'm pretty sure your teacher wants you to understand whatever code you hand in. If you do understand the code, then you would know if the book is correct, or if you have introduced own errors or if the code you have is actually correct as is.

Assembler programming isn't black magic. It's just a question of doing everything one step at a time - just as the processor does it - and to keep track of what the input is and the output will be. And what further changes are needed until the output have become as expected.