The name is written nfr plus tm and both halves are ambiguous. It is read as "Atum is beautiful", making the god a statement about the creator, and it is read as "the beautiful one who closes", making it a description of the lotus shutting at dusk. The two readings imply different theologies and Egyptological reference works give both without settling between them.
What would resolve this An early attestation where the name is written with a determinative or in a context that disambiguates tm as the divine name rather than the verb, or a demonstrably early orthography that rules one reading out.
OpenEgyptology, philologyDonald B. Redford (ed.), The Oxford Encyclopedia of Ancient Egypt