Npc's Dialog Options

Yellow Stat Exchange: The top option, "Yellow Stat Exchange", is the option that initiates the yellow stat exchange, taking your bad yellow stats and giving you a good yellow stat.
Orange Stat Exchange: The second option, "Orange Stat Exchange", is the option that initiates the orange stat exchange, taking your bad orange stats and giving you a good orange stat.
Ask for details: Full list of good stats it can give you.
Ask for information: This is the option that directs you to this page, for detailed explanation.

How can I exchange stats?

Place the 10x useless stats you received as a 'Mana Stone Tier 6' somewhere in your inventory, as shown in the image below. Check which stats can be traded by using the 'Ask for information' option of the NPC..
Note: Please remember that the type of stat you wish to exchange will be taken into account. If you want to exchange a yellow stat, make sure to collect bad yellow stats! Or, if you want to exchange your orange stats, make sure of that as well.

If you are sure that you have met all the conditions, talk to the NPC again and click 'Yellow Stat Exchange' if you want to change the yellow stat, or 'Orange Stat Exchange' if you want to change the orange stat, and they will take your bad stats and give you a good stat in return, as well as exchange your bad stones for a flower.

What are good stats?

The three option, "Ask for details", shows you the good stats you can get in detail.