This is not an error of duplication. The full-fledged version of this Mitzvah are many and change for those who are learning the one/three chapter a day.
Positive Mitzvah 5
Worshiping G-d - "Prayer"
Exodus 23:25 "And you shall serve the L-rd, your G-d"
Imagine a magnificent palace with servants always ready to serve the king. Some stand by his throne, others bring him food, and, still others, tailor his velvet robes.
This service is fit for a king.
HaShem is the King of all kings! He does not ask us to perform these types of service, but rather instructs us to serve Him through Prayer Tefillah.
As subjects of our King, we express our dedication and loyalty by offering our praise and making our requests through prayer.