It is understood that 5.4^0 is the number 5.4 raised to the power zero.
There is a rule for this: any number raised to the power zero is 1.
So, 5.4 ^ 0 = 1.
You can show that any number raised to the power of zero is 1 using this:
A^0 = (A)^(m - m) = [A^m] / [A^m]
Given that the numerator and the numerator of that fraction are equals the result is 1.