The first couple of years, I bought daycare groceries separately and claimed those receipts 100%. However, it wasn't an accurate number because they would often get our leftovers, which was a lot of the meat and when I baked, that stuff was out of our personal groceries most often.

Now I just buy everything together, tally it up and claim half (that's the number I get to claim for most things) because half my house is daycare dedicated. It made a significant difference to my deductions