Counting Children Rows

Fialko66

Can anyone advise how to count children rows please?

I have tried several examples from the net but none seemed to work, though i did get this

=COUNTIF(CHILDREN(), 0) + "" to work for one row (without the additional criteria of checking if a checked box was checked) which gave the correct number 3. when i converted this to a column formula the 3 changed to 0!!

I just need to count open children rows for a report but can't figure it out which replicate when i convert to column formula

Thank you

Barry