What does waiting "in two lanes" mean?

Libraries may buy extra copies of a title and share them with other libraries in the consortium. When you place a hold on a shared title like this, you may see a note that you're waiting "in two lanes." One lane is for the consortium's copies of the title, and the other is for the extra shared copies.

The library who bought the extra copies prioritizes their patrons' holds on those copies. So, their patrons will have their holds filled first when one of those copies becomes available. You'll still have your hold filled, but your wait may be longer or shorter than estimated, depending on which lane you're in.