Same here 
I just fired up my nRF24 module for the first time since I got them some years ago. From what I gathered in the code, the first and second row simply indicates that there are 126 columns, representing 126 nRF24 channels (I guess). Then the rest of the rows are signal strength received in each channel. From your data, signal is strong around channels 0x40 to 0x4A and no signal in other channels.