Access Top and Right Variables from RectTransform

Hello there, i have googled a lot about this topic but i cannot get it right.

I create a new GameObject called Panel, and I add the following Components to it:

panel.AddComponent(); panel.AddComponent(); panel.AddComponent();

the next step was, to change the anchor Min & Max to my Custom settings, this worked fine, but if i want to change the Left/Bottom/Right/Top Values with:

panel.GetComponent().offsetMin = new Vector2(10, 20); panel.GetComponent().offsetMax = new Vector2(-30, -40); (because i read that they are inverted)

I can only change the offsetMin. My offsetMax dont get any changes.

Any Ideas?