Career Level Tuning/Sim Data

Hello. I don´t know, where can I ask this question, now, I write here, it is my last option. If I download some career, custom, or original TS 4 career I add to Package, there are 2 folders. Career Level Tuning and Sim Data, where are written same informations, which I can found in Career Level tuning too. Such as, salary, Work days, etc. And my question is. How difference is between Career Level Tuning and Sim Data, if in both folders are written same informations, about concrete career level. Can you answer on my question, because, example, I change salary in Sim Data (<V name="pay_type" variant="0xDED374D3">

<T type="Int32">52</T>

</V>) But in game, isn´t this change, only if I change it in Career Tuning. Why exist Sim Data files, when I can´t change informations in it. I can change example, name of Career Level, in Sim Data, but no salary, why? Very thanks for help.