The time axis is in seconds.
This time-frequency plot (sonogram) clearly shows the pitch lines and the main resonances around 3000 hz and 6000 hz (48 khz and 96 khz for the bat).
Closeup of one of the pulses. One can count 14 cycles in a bit less than 0.005 seconds, corresponding to a frequency a bit higher than 14/0.005 = 2800 hz. If the detector divides by 16 this is a bat signal a bit higher than 44800 hz. This matches the sonogram information, as it should.