This need to be rechecked, but i have heard that:
pingtest doesn't use actual traffic - it sends small packet (64 byte) and then sends big packet (1518 byte) record the latency difference. Lets say small packet was delivered after 5ms, big packet after 9ms. so in essence 1518-64=1454 bytes were delivered in 4ms (Google is saying 1 bytes/millisecond = 0.00762939453 Mbps) so we get that link speed is 2,77Mbps, but we actually used only few packets.
Not the most precise way to check your limits
- use popular torrents, lets say some freeware Linux distribution (wave to ACTA), to check your queues.