Under Falling Skies unfortunately lives up to its name

I am reading the rules pdf (2.0) Am I the only one having issue with understanding this rule

You will place two white dice, so you must reroll twice – or only once, if you save a white die for last.

No example, a simple sentence for a pretty important rule. I did not get what I reroll twice. I had to watch a rules video by Paul Grogan to get it. I thought I would reroll white dice, but no, you reroll all unplaced dice. Maybe for native english speaker it is clear?