If the $1,287 was the total amount of your refund (both federal and state together), the $730 you received might reflect just the federal or just the state. These refunds will arrive in two separate transactions because they are handled by two separate agencies (the IRS and your state tax agency). 

If this was for just one refund (federal or state) and the amount was less than what was submitted on your return, this means that they could have made a change to your return that has impacted your refund, or they could need more information to finish processing part of your refund. Another possibility is that it was partly taken in order to offset a prior debt owed.

In all of the situations above, you will receive a letter explaining exactly what happened, what additional information they might need (if any) and contact information. You could also call the IRS or your state tax agency before receiving this letter, they might be able to access your account and explain what happened.