there's no easy answer to this as it's not a straight forward calculation.

Think of your delegation as contributing to a voting-power-pool. This pool is then able to vote on dust and you will get at least your fair share when you need it.

As the vote value constantly fluctuates how much dust "your share" is able to cover fluctuates accordingly.

Since voting power also has a strong time component the bunny tries to min max it's available power as fairly as possible amongst it's supporters.

This is being kept track of with bonus priority minutes for your delegation and an offset deducted for the dustvotes you've already received recently.

As the bunny owns a good bit of stake which it counts towards its users on top of the pooled delegations, I think it does always generate a fair value back for the delegations.

You can theoretically fine tune your delegation towards your dust demand via the bunny's discord interface... it's just unfortunately not very straight forward due to all the voting-maths and all the fluctuating variables