Less than half our time is spent gaming on smartphones than on texting.
According to the book in which this statement was published, this sentence means that the time which is spent gaming on smartphones is less than half the time which is spent sending emails. (the book is written by a English teacher from Japanese.)
For example: gaming on smartphones ⇒ 1 hour , texting emails ⇒ more than two hours (per day)
I think that the word "than" needs to be preceded by a comparative class or specific word(e.g. other, rather, and so on). So I thing that this sentence is incorrect grammatically.
What do you think about my idea?