lerfu pro-sumti followed by number gotcha
Mentioned in the Book, chapter 17, section 9, example 9.7.
The dog spoke "Arf." It barked once.
le gerku cu bacru zo .arf .i gy. paroi cmoni bzzt
Correct is le gerku cu bacru zo .arf .i gy. boi paroi cmoni
gy. pa is one lerfu-string, so gy. pa roi doesn't parse. It can be split into a lerfu-string plus a number with gy. boi pa. It is easy to forget to add boi when you drop in a number or a second lerfu pro-sumti after one lerfu pro-sumti.
Some may see this as a reason to prefer KOhA pro-sumti over lerfu pro-sumti. (See lerfu pro-sumti, and why ko'a sucks.)
If you aren't going to say enough to make goi ko'a worthwhile, try le gerku cu bacru zo .arf. .i ra paroi cmoni