hat LED will blink if there is any Internet traffic communication(if you do surfing). Sometimes your LED keeps glowing even when you dont do any surfing, at that situation your system softwares, say Antivirus or other, might be contacting their remote server to download patches or so.

So what your engineer told is false (i dont kno whether you communicated it properly to us). You should not assume that you are utilising Full bandwidth just by seeing LED blink.

LED blink shows that there is some internet traffic flow in the modem thats all nothing else.