ADC conversion microchip

i am trying to read 4 analog signals connected to micro chip dspic30f4011 and i am really confused with the conversion mechanism. I decided to read the 4 channels sequentially using channel 0. But my doubt is with the register SMPI<3:0>. The data sheet says it can vary from 1 sample per interrupt to 16 samples per interrupt, what it actually means? If i want to read 4 analog signals to what value shall I set will it be 3 or 4? And can i read it from registers ADCBUF0 to ADCBUF3? Please help.

What is the values range the register can take? Usually, MCP is clear explaining registers usage.