In English, calculus and calculation are two different things. And there are a number of grammatical errors in that sentence that make the meaning unclear.
I'm noting this because if the teacher allowed you to do simpler calculus so long as you maintained an error margin of 10%, that's different from allowing you to do simpler calculations provided you keep an error margin of 10%. Calculus is specifically the branch of mathematics involving limits, functions, derivatives, and integrals, and from the English it sounds like she, if we are being perfectly pedantic, was giving you the option do do approximations with your integrals and derivatives, not with any value you like.