I’m trying to tween this ui and make it so that it slowly increases in size from the bottom to the top like this:
but instead, this happens:

They appear to go downwards. i assume this is because the position is not being changed.
anybody know how I can calculate what the position should be set to or an efficient way to resolve this issue?
Try setting the AnchorPoint Y to 1
nope

i found a hacky way to get it to work; uilistlayout and set to top mid or bottom. but I want a way to do it without it in case a uilistlayout needs to be used for another purpose.
Based on what you are trying to show in your video, as someone else had pointed out you can achieve this using AnchorPoint.
i.e. AnchorPoint 0, 1
Position = 0, 0, 1, 0 (should usually not change)
Then size can be tweened as normal, and will be tweened from the bottom up, instead of top down. Unless maybe I am misunderstanding your intentions?