It's a much trickier question than you might expect.
The first point to understand is how bid-bots operate. A bid-bot will (typically) vote on a 2.4 hour cycle. At the end of the 2.4 hours one of the bots 100% upvotes will be split between all users who have sent bids, in proportion to the value of the bids they have sent.
So on the main page of steembottracker the "vote value" in the second column of the list of bid-bots is the (estimated) value of the bots 100% upvote. If you were to be the only bidder, that is the full vote value that your post would receive (for a bot with no capping). This column provides a view of the overall value of the market on which you are bidding.
Within the "Actions / Details" section of each steembottracker-listed bot the "vote value" shows the current estimated vote value that you will receive based on your bid and the other bids made so far in the auction. This should be a high value at the start of the auction and decrease towards the end of the auction as more bids come in. However it is also worth noting that this vote value is affected by the ROI cap imposed by many bots (so it will be capped to 10% more than your bid for a bot with a 10% max ROI).
Another complexity is that the vote values can be expressed in 4 different currencies:
- USD, SBD, STEEM and STU (post rewards).
As such the vote value is the value of the upvote re-expressed in one of these currencies.
Always make sure that you understand which currency you are working in.
Good luck!