What are the head diameter and head minimum dimensions referring to for flat head screws when adding a new fastener size to toolbox?

I am adding an M2 flat head size to toolbox in SW 2014 and SW2017.

Does anyone know what are the head diameter and head minimum dimensions

are referring to for flat head screws when adding a new fastener size to toolbox?

I looked up dimensions with respect to the DIN standard.

https://www.brightonbest.com/catalog/UK/Socket_Screws_Metric.pdf

Can't find any details of this anywhere.

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