They turned the pages, which were yellow and crinkly, and it was awfully funny to read words that stood still instead of moving the way they were supposed to -- on a screen, you know. And then, when they turned back to the page before, it had the same words on it that it had when they read it the first time.
`Gee,' said Tommy, `what a waste. When you're through with the book, you just throw it away, I guess. Our television screen must have had a million books on it and it's good for plenty more. I wouldn't throw it away.'
Please rephrase the highlighted sentence. [Particularly I can't understand because of `must have had']
I never come across a sentence with (must have had)