The 25% odds are per egg. The more eggs you hatch the more likely you are to get 1 or more pied. So feed that girl well!

The formula to figure out your chance of getting at least 1 pied would be 1 - 0.75^N where N is the number of eggs. Basically you are figuring the cumulative 75% odds that each egg will miss and be normal and subtracting it from 1 to find the odds of all the other outcomes where at least one of them has an albino.

So if you had a 4 egg clutch your chance at least one of the eggs contained a pied would be 1 - (3/4)^4 = 1 - 81/256 = 175/256 or about 68%. If you can get the girl up to 8 eggs size your odds of hatching at least 1 pied go up to almost 90%. It never gets to be a 100% guaranteed thing but with more eggs it gets closer and closer. With 16 eggs from het X het it’s up to almost 99% chance you will get at least one pied.