DSA 5 Sheet (GER) Q: For what did I roll when I roll "F" within the talentsheet?

Hey, Ive searched already for the answer, but I cant find anything. Hope someone could give me an answer. For what is the roll on "F" (Fertigkeitsspeziallisierung/skill specialization) within the talentsheet?

it's rolling using the special ability : Skill Specialization () The hero can specialize in certain applications of Skills . Many skill descriptions mention applications, but not necessarily all that are available for that skill. Ask The GM about others that may exist. Example: A hero wants to specialize in Magical Lore. The player chooses the application of Spells . Whenever making a check using Magical Lore (Spells), raise the hero’s SR by 2. it's linked with this ability. You can look the formula for the rolling in the chat, with your mouse cursor over the result of the roll sorry for my poor english i m french

Thank you!