9.99..... E307 is the largest number Excel can handle. I gave you a comprehensive formula (meaning whether there is a numeric entry in the list, or some text entry), the formula will pick up the last entry in the list.
Let us get to your particular case ...
1. what are the entries in your list, TEXT, or NUMBERS?
2. what is the range of your list ... do you know the starting cell, the ending cell, do you have a NAMED RANGE, or all you know is that it is in a particular column (in that case which COLUMN?)
If you can provide information for the two items above, we can pin down the formula more closely for your case.