It is beneficial to reward good publishers extra, so that they will promote your affiliate campaign even more. As an advertiser, you can also stimulate publishers by rewarding them extra from a certain number of transactions (applying a tiered scale); this concerns transactions on a monthly basis.
You can not set or adjust compensation groups yourself; your Daisycon contact person does this for you. Your contact person can also advise you on the right setup for a tier.
How do I determine the compensation of my affiliate program or lead campaign?