The soil type is an important part, in that it give a figure for the Available Water for in/in (or mm/mm). This is essentially the souls ability to store water. I had a clay selected, but I could not have been more wrong.
I did a “Mason Jar” test (plenty of YouTube videos) and my soil is basically totally sand, so my setting has dropped from about 0.20mm/mm to a new low of 0.05mm,/mm. No wonder our gardener had to add extra water to zones this summer.
It would also have a huge impact on the calculated runtimes. There’s no point in watering for an hour if a huge amount would just drain away.
This link is good