What are you looking at ??
34 Mega bits per second on speedtest (Shows speed in bits per second )
34/8 = 4.25 Mega Bites per second
My IDM is showing 4.474 Mega Bytes per second. (IDM shows Bytes per second)
(if you are going to take the difference b/w 4.25 and 4.474 Mega Bytes per second as "Doesn't look very accurate to me." than i really can't say much)
Note: There are 8 bits in one Byte hence the divide by 8