Calculating Maintenance Advice

I've been paying a family based arrangement every month to my ex partner ever since the birth of my 11 year old daughter. To calculate it we used the Child Maintenance Calculator found on the Government website.

I now have a new partner, we are still together and back in April she gave birth to another girl, so now I have two children to pay for.

I now plan on adjusting the maintenance I pay to my ex partner who is the "parent with care" of my 11 year old to reflect the fact I now have another child to pay for and am using the Gov calculator again to work out a figure.

When using the maintenance calculator should I say I pay maintenance for two children now where the first question asks "How many children do you pay maintenance for?" as I don't actually pay maintenance to my current partner we just contribute together as we go along.

Also she has 3 other children that are not mine but live in the house full time, do I put these children down in the question "How many other children live in your household?" as I don't contribute directly to these children's upkeep.

Any advice gratefully received.