If something is done tolerably, it means it's done well enough to be acceptable, like cooking a meal that is not mouthwatering or amazing, but still edible.
When you read a book and come across a few confusing parts, you might still understand the story tolerably well. Similarly, if you complete a project at work that meets the basic requirements but isn't your best effort, you've performed tolerably. The word tolerably can also describe how you might handle a long meeting. Even if the topics are boring, if you stay engaged and get through it, you’re managing tolerably.