In the purest since an egg that does not hatch is a failure. eggs fail for many reasons. So in that case you have 25 of 47 or 25/47. The (/) sign means divide. 25 divided by 47 is 0.532 or a 53.2% hatch rate. Now that would give you a complete picture of your success with eggs and all mishaps or infertility issues etc. if you are trying to target a specific portion of your success, say fertility percentage then you just take the number of infertile eggs and divide that by the total of eggs etc. If you are trying to figure out how well your bator is working you might want to only use the number of eggs that started developing as the total number of eggs set.
In this case 3/47 or 6.4% loss due to bator design.
11/47 or 23.4% infertility
25/47 or 53.2% Hatched
leaving 8/47 or 17% not known yet
If you want to know how well your bator did and remove all infertile or broken eggs it is then 25/33 for a 75.8% hatch rate and counting. Not bad, now you just need to get your roo in gear and remember eggs are fragile and you are top drawer.