Over 300 million books vs. more 300 million books

[Kleopathra]

English Grammar Tests, Elementary Level

ESL/EFL Test #103 "Agatha Christie test questions", question 7

Agatha Christie wrote more than 80 mysteries and sold ......... 300 million books.

(a) more
(b) extra
(c) over

English Grammar Tests, Elementary Level

ESL/EFL Test #103 "Agatha Christie test questions", answer 7

Agatha Christie wrote more than 80 mysteries and sold over 300 million books.

Correct answer: (c) over

Your answer was: incorrect
Agatha Christie wrote more than 80 mysteries and sold more 300 million books.
_________________________

why not use more?

Kleopathra

[Yankee]

.
If you wanted to use more in the second half of this sentence, then you would also need the word than -- the same as in the first half of the sentence.

Using over in from of a number means the same thing as more than:

- over 300 million books = more than 300 million books
.