Each ad format has different minimum and maximum rates.
You can place your bid in accordance to the suggested rate card, Which you can also find on the panel: http://ad-maven.com/Recommended%20Rate%20Card.html
Push Notification CPC:
Minimum: 0.0002$ (Translates to 20 Cent CPM)
Maximum: 0.05$ (Translates to 50$ CPM)