Size avatar on postbit

[Delja]

How do I set the avatar to match the bottom of the postbit, how do I actually extend it?
To note; I set the avatar size for administrators to 225x400 but it shows me a few sizes smaller avatar image on the postbit ..
More in the pictures below ..
:(

now
https://i.imgur.com/CABh6tV.png

i need this

https://i.imgur.com/MImjFWZ.png