A correct example would be to transpose the placeholders in pattern 2.
This is typical where changing messages from one language to another changes the word order, to result in a sensible translation.
Let's imagine it's localised as Spanish or Russian instead of English.
So really you want to have pattern 2 provided by your human translator to read like this :
New pattern: '{1,number} trees hosting {0,number} monkeys'
Formatted number: 456 trees hosting 123 monkeys
That is - the order of arguments is always the same, but your translated message content has the placeholders transposed for non English languages.