Ace step 1.5 xl size

I'm a bit confused about the size of xl. Nornal model was 2b and 4.8gb in size at bf16, both the diffusers format and the comfyui packaged format. Now xl is 4b and I read it should be ~10gb at bf16, and it is 10gb in comfyui packaged format, but almost 20gb in the official repo in diffusers format.