How do Update Flight level

[Adi-18]

I have a flight plan from world view. It's a short fly, so my level has to be 5100 ft.
But MCDU shows FL 200. Absolutely wrong.
How can I reassign FL for my short fly? In [Init] its on FL051

[tracernz]

These are altitude constraints coming from the STAR you have selected (BLM3G). You can select a different STAR, or delete the constraints (although you will no longer be complying with the STAR if you do that).