I don't know how you calculate it on the MMS calculator, but on SoapCalc, underneath the field that says "Water as % of oils", there is a check box after the words "Lye Concentration". You check that to tell SoapCalc that you want to set the define the Lye Concentration you want. And you would put 40 in there. But keep in mind that many will suggest that 40% Lye Concentration is really for those with some experience under their belt. In fact, anything stronger than that and SoapCalc will give you a warning.
Basically, there are two ways to use SoapCalc regarding water. Both end up with the same result. But you must be clear about which one someone is talking about when they give you info because they have opposite meanings. For example, the default water as % of oils is set to 38. But when you view the recipe on the second page, it'll tell you what Lye Concentration that is. I just did and it says 24.8996%. To get to a strong Lye Concentration like Soapbuddy uses (40%), you'd have to use close to 19% water as percentage of oil.
Does that help? Or is it clear as mud?

zeo