Well, DTR is the amount of data to be transferred from one location (device) to another location (device). DTR varies from devices to devices and also if we are transferring serially or parallel.
For example, the DTR of an external hard drive using usb2 can be max up to 480Mbps comparatively to this - same hard drive with USB3 could transfer 10 times more data. DTR was initially measured in bps (bits per second) but now it reached in Gbps (gigabits per second).
i hope this will help. if you have any questions, please post here and i will try to answer. --Amber