Please note that Sprintax Calculus and Sprintax Returns are two different types of software. If your institution has a partnership with us they may both systems.
Sprintax Calculus (https://calculus.sprintax.com/) is a pre-tax system used by your institution to gather information about any income, residency, tax treaty and other details, so that they could know which documents to issue and ensure they are issuing the correct documents.
Sprintax Returns (https://www.sprintax.com/returns/) is the self-preparation tax return software that you may use to prepare your 1040-NR Federal tax return, State tax return, Form 8843 or FICA refund claim form which you will need to file to the relevant US tax authorities.