Macros relate to ⅛th of sponge, on the assumption that you wouldn't eat the whole lot in one sitting... ;)
For the entire 300g just multiply each value by 8.
Metric kitchen scales are an inexpensive yet invaluable gadget to enable accurate measurement of ingredients. Store them upright in a cupboard or over your worktop and they'll only take up a tiny bit of space. Click
HERE for the ones I use in the UK. For U.S. option click
HERE.