It is fixed amount of Golos you define in memo field when transfer your donation fund to Dobrobot account. Dobrobot has no caps on it, I think, but it is not a problem to add such caps in code. It is better to deploy such bots by trusted person in the community. Dobrobot uses its active key to transfer funds.

For example, I transfer 100 Golos to @dobrobot with memo: 5.
This means that on each my upvote @dobrobot will send 5 Golos to upvoted account. So I have 20 upvotes before I get a message Your donation fund is empty, please refill.

Anytime I can change this Golos per upvote number to 10 by transfering minimum 0.01 Golos with memo: 10.

I'm just the author of the idea. The developer of the bot is @ropox.

Useful links:
https://golos.io/@dobrobot/transfers
https://gropox.github.io/dobrobot/?dobrobot=dobrobot&minBlock=5691376
https://github.com/gropox/dobrobot
https://web.telegram.org/#/im?p=@chain_cf