Your if and else clauses are both incorrect:
if (number1 < 0);
printf("Must choose a number greater than 0 or below 25");
else (number1 > 25);
printf("Must choose a number greater than 0 or below 25");
So the correct code would be:
if (number1 <= 0)
{
printf("Please choose a number greater than 0 and below 25");
}
else if (number1 > 25)
{
printf("The number must be less than 25");
}
or perhaps a simpler version:
if (number1 <= 0 || number1 > 25)
{
printf("Please choose a number greater than 0 and less than 25");
}
Note, it is a good idea always to use curly braces around blocks of code following boolean expressions. Even though the block is a single line, it is a good habit to cultivate.