Does "calcified dural plaque versus small non-enhancing meningioma" mean it's either plaque or meningioma? i don't understand the use of "versus"

Versus a : Calcified meningioma? Its probably too small or atypical to distinguish. Second opinion from a neuroradiologist versus a neurosurgeon is suggested, versus repeating the study in 3-6 months.

Differential Diagnos: When an x-ray (MRI) is read, the radiologist does not have an exact diagnosis of what is being evaluated. The doctor will give a best educated evaluation, but will also give a differential diagnosis. This diagnosis is what a lesion could possibly also be.

Versus: As you correctly thought, it means that the interpreting physicians thinks it could be one or the other. They can both look very similar to one another.