I found this sentence online and it had no reading to it. So I presumed that “10” was read as とお considering how this number is counted within the つ counter group.
However, I wasn’t sure so I asked a Japanese person whether it was really とお or maybe じゅう and they said it was indeed じゅう, but they couldn’t explain why. I was wondering if anyone knew? Is it perhaps that no counter is necessary in this sentence? If the number in the sentence was 9 for instance, would it be read as きゅう or 9つ as in ここのつ?
Thanks in advance