Simplify the following text for a Grade 10 native English-speaking person.
Original: The discovery was announced ( IAUC 4867 ) on September 29 , 1989 , but the text only talks of `` 25 frames taken over 11 days '' , giving a discovery date of sometime before September 18 .
Simplified: The discovery was said ( IAUC 4867 ) on September 29 , 1989 , but the text only talks of `` 25 frames taken over 11 days '' , giving a discovery date of sometime before September 18 .