correctable error?

[welref]

B1 is fouled by A1 during a field goal try with 3 seconds remaining in the 4th quarter.Team A is up by 2 points. By mistake, the official steps in and says 1-1 instead of 2 FT's. B1 shoots the first FT and misses the FT attempt. B2 secures the rebound and scores a 2 pt basket on a tap before time expires. AFter time expired to end the fourth quarter, the scorer then notifys the referee that B1 should had shot 2 FT's instead of a 1-1. The referee then begins the OT period by giving B1 his second FT and play continues from there. Was this correctable error administered properly? Rule reference for this sit. will be appreciated.