Setting initial fossil age BEAST2

[Ivan Ayuso-Fernandez]

Hi all,

I'm following the tutorial from taming the BEAST "Divergence Time Estimation using BEAST v2.*; Dating Species Divergences with the Fossilized Birth-Death Process"

https://taming-the-beast.org/tutorials/FBD-tutorial/

There is one thing I'm not getting. In page 11 of the pdf, when explaining  how to set an initial value for the age of each fossil, the example of Kretzoiarctos beatrix is given. It says that the fossil has an age between 11.2 and 11.8 so the initial age is set to 11.7. I saw that for the other fossils in the tutorial, the initial age will be between max and min ages, but how is that age chosen?

I have the fossils needed to calibrate my species tree with their min and max ages, so thanks in advance for answering this silly question!