It's a pain because squidrabbit's tissues are what get measured and will always be 46, not the character's true measurements (except for breast measurements for some reason). The first day should be an immediate true size increase that you won't see. It may increase again but If it does it's likely from a different flag all together.
Please reference the long breakdown provided by Unnie on the feedback and suggestions thread for a better idea of how sizes increase and decrease.