How to truly export a spritesheet into grid format?

hello aseprite community, love this program it’s my best pal but i’m a little confused how to make it do what i want when it comes to exporting sprite sheets for my partner to use in unity.

what we want:
ideally i’d like to be able to export my sheet of ui elements so that every element is centered in a grid square of 64x64. so like, if you were to put a grid over the entire sheet every sprite would be in the center of their little squares. that way, when she imports the sheet into unity she can use the slice function to auto generate the sprites within their 64x64 bounds.

however the grid feature in exporting sheets doesnt seem to do that? some sprites seem to be in the middle of two squares and i’ve tried every setting i can think of but nothing seems to fix this specific problem, and i’ve run out of settings combinations to try haha. (all the sprites are well under 64x64 pixels)