This is a pair of polarity items. One appears in positive contexts, the other in negative:
イギリスの ジャムは とても おいしいです。
イギリスの ジャムは あまり おいしくありません。
Every language has words like these. For example, in English:
I like pie, too.
I don't like pie, either.
Here, too and either are polarity items. In our positive sentence we use too, and in our negative sentence we use either. It doesn't work very well if we reverse them:
×I like pie, either.
×I don't like pie, too.
We can see something similar in your Japanese sentences. とても means "to a great degree", similar to English very, and in this meaning it appears in positive contexts:
イギリスの ジャムは とても おいしいです。
English jam tastes very good.
On the other hand, あまり means "to a low degree", similar to English not very, and in this meaning it appears in negative contexts:
イギリスの ジャムは あまり おいしくありません。
English jam doesn't taste very good.
Your book probably didn't mean for you to put them together into one sentence.