That is probably the article's typo. At least it is not what was read into record.
Hemlock
joined 1 year ago
Amount is for things you cannot count. For example, an amount of water. If you can count it, use number of.
HOWEVER, English is not a dead language, so the definition of amount may just be changing.
Thank you for using "number of" instead of incorrectly using amount as is the current trend.
Not for long if you keep looking at the sun