hiya yes bought one of those too, and to be honest, found it crap!!! 🙁 didn’t seem to show major differences any days etc, still have it here stuck in the cubbord!
but i bought the clear blue fertility monitor, and its the business, well worth the money, you can buy them cheaper on ebay too, but 3 kids later here!!! it works , month 2 with first and month 1 with the other 2!! so defo invest in it, sorry about the other thing not working for me, don’t want to be negative, but know a few who got it and it never worked either… 😥