That is strange indeed. Where did you find "i have not 1 pool." ? Was it actually with a lower case "i" and the numeral "1".
Was it on Android, iOS or the web? What kind of exercise was it...Strengthen skills, multiple choice e.g.?
We do not have anything like that in our incubator.
same happened to me, working on a laptop (windows 10) it was not lower case "i" but I but it was exactly: "I have not 1 swimming pool."...
Same thing from a laptop running windows 10. I have no 1 swimming pool. Do please correct that! Is annoying that you have to learn the mistakes in order to perform well!