Whenever number less than 1 is raised to the power of "t" , the equation is exponentially decaying. This is because as time increases the decimal is being raised to a higher and higher power causing it to decay. For example, when t= 0 sec in eq 1 the H= 5.9(0.82)^0 = 5.9(1). So, at time= 0 seconds H= 5.9. but, if time increases to t=2secs, then H= 5.9(0.82)²= (5.9)(0.6724)= 3.96716. At time = 2 seconds H= 3.96716.
In the other case, where a value greater than 1 is raised to the power of time(t) the equation is an exponential growth equation.