10 years ago most of our time in front of screens was spent on TV and computers. As smartphones and tablets have come into play though, they've come into direct competition with TV and computers. A smartphone or tablet can essentially be a TV and handle many of the tasks done on computer so it's understandable why people are spending more time on them.
It's interesting to see how the minutes spent on a platform can differ massively across countries. The UK and USA spend much more time in front of the TV compared to countries like Vietnam and Thailand.
You may also expect countries like the UK and USA to also spend more time in front of screens because they're much more developed, but Indonesia and the Philippines are well ahead.