Max 10 unused VREF's

Hi,

You can actually set the unused pins as "Input tri-stated with weak pull-up" from Quartus II setting

Goto "Device and Pin Options" -->Unused Pins --> Reserved all unused pins: As input tri-stated with weak pull-up"

Here is the link from Altera can be your reference:

https://www.altera.com/support/support-resources/knowledge-base/solutions/rd10192006_240.html