I wonder how is the high order exponent calculated when the number is relatively small. For example, 8 exponent when the number is only 10^10^10. Taking log 3 times gives 1, then 0, then log 0 is undefined.
If the number is too small for that many logs (i.e. the value would drop to 1 or below before the last log), the upgrade simply does nothing and leaves the number unchanged, so log 0 is never evaluated.
