Volume-wise you're right that smaller volume will lead to smaller grow, you should measure the "whole pot", aka the reservoir... but i think i'm seeing problems already, the seedling is not doing well, you want to check that PH, and make sure that seedling is getting what it needs, i would try to save it, but it looks like it will be stunted as it is, and i guess that it will stay small because of that. Just see for yourself ! 🚀