I have bid on upgrades three times. The two times it was accepted, the bids showed in the "weak" range. The other time (also in the "weak" range) it showed pending for the last week when all other bids had "expired." But someone must have made a new booking during that time, so I didn't get the upgrade.
So, don't worry about where it is in the range - bid what you are comfortable bidding, and be pleasantly surprised if/when you win!