As it happens, I own a copy of Atlas of World History, Rand McNally, ISBN 0-528-83779-6, and on pages 76-77 it has a map of "the Manchu Empire at its Height" - the Qing Dynasty of China c. 1800.
The map has several concentric and very roughly circular lines dawn around Peking (Beijing) and each line has a number. The number specifies the "maximum number in weeks for a mounted courier from Peking". Presumably if couriers took longer than the specified number of weeks there would be trouble for the responsible members of the courier service.
And of course the average number of weeks, and the minimum possible number of weeks, would be shorter than the maximum number of weeks.
On the map sale about 500 kilometers is about 37 millimeters, so 700 kilometers should be about 51.8 millimeters, and 1,000 kilometers should be about 74 millimeters.
Going north to Manchuria, 700 kilometers would be a bit beyond the 2 week limit, while 1,000 kilometers should reach the 3 week limit. Going south into China, 700 kilometers would not quite reach the the 2 week limit, whle 1,000 kilometers would be between the 2 week and 3 week limits.
Of course, imperial couriers could sometimes travel faster and reach places in less than the maximum times listed on the map. And travelers who were not imperial couriers would probably not be able to travel as fast as imperial couriers.
And as I wrote in a comment: 1500 BC would be ancient China. AD 1500 would be late medieval or early modern China. We may doubt that there was a mounted courier system during the Shang Dynasty in 1500 BC, and of course back then someone might not be able to travel as far as 700 or 1,000 kilometers without leaving the territory of the Shang Dynasty, and thus the region served by any hypothetical Shang mounted courier service.
Added 04-15-22. Urgent messages were carried in saddlebags on horses ridden by the couriers if they had to get somewhere fast. Eech courier would ride and drive his own horse. Ordinary mail might be carried in mail carriages or mail wagons pulled by horses, which sometimes might also carry passengers, depending on which organization operated the mail service, and would travel much slower than single horses ridden by single men.