Hi Tab,

You have four digits to work with and six positions to fill so there are

\[4 \times 4 \times 4 \times 4 \times 4 \times 4 = 4^6 \]

ways to produce a six digit string from the four digits, 0, 2, 5 and 8. However some of these strings like $022508$ and $000852$ do not represent six digit numbers since, as numbers, $022508 = 22508$ and $000852 = 852.$ If one of your six digit strings is to represent a six digit number its leftmost digit can't be zero. Hence there are only three choices for the leftmost digit in the string and hence the number of numbers is

\[3 \times 4 \times 4 \times 4 \times 4 \times 4 = 3 \times 4^5\]

Penny