This piece uses hexadecimal (base 16) numbers, so you will see the letters A through F.  It is related to an earlier piece subtitled "Big Red" that also uses transparent domes over the numbers and "Binary Bubbles" that uses binary numbers (only 0 and 1).  The earlier pieces used surplus red and green plastic domes, but I had to fabricate my own blue domes for this piece as blue ones were unavailable.