The i7600s RTA function measures the channel 1 and 2 inputs at a sampling rate of 44.1 kHz / second. The individual frequencies are separated as indicated on the front panel (listed horizontally), and the last bar of each channels RTA is known as the all column (meaning it displays all frequencies signals together).

All results are given in dB, as listed horizontally. The RTA function doesnt measure room acoustics or speaker performance, simply the signal you send through the inputs.

For extra detail, individual frequencies can be scrutinized if you rotate the left-most control (the frequency bar will flash to show the frequency is highlighted).  Pressing the control in will allow the i7600 to display the details of the frequency band in detail on the LCD screen.