From the introduction:
Descriptions of the lives and accomplishments of those leaders known to have ruled the New Rocto-Ardae Empire for approximately the last two thousand years. An important fact to remember when considering the lifespan and reign of any Emperor, is that a year on Telostic is 500 days of approximately 25 hours each; for example, an Emperor of Roctien who has ruled for ten Telostician years, would have been in power 14.24 Earth years.
The descriptions of many of the Emperors, particularly the early ones prior to the First Osche Dynasty, are incomplete; historical records of the early years of the Imperium lack details in many important areas. Many of the Emperors (cf. Gnuga X) do not first appear to recorded history as the first of their namesake. There are various reasons for this, usually previous namesakes having controlled semi-independent fiefs, but in some cases there is no known explanation.