No checks are done on the content of the cDNA field. The placeholder suggests the format c.1094C>T, however the user is not in any way constrained to follow. Even if the suggestion is followed, the user may introduce leading or trailing spaces (e.g. by copy-pasting from a report). This prevents proper checking for unique variants.
For example, in theory we do not allow the user to enter the same variant twice in a patient record. however, the user may enter c.1094C>T for one variant and c.1094C>T<space> for the next one, overcoming the uniqueness check.