Enable Show Audio Time Units, and now try zooming in on your timeline. Premiere has switched to a sample-based timeline, allowing much more precision for fine-tuning audio. Toggle the menu option off to return to a frame-based timeline when you switch back to editing video.

Be aware of any linked clips, which means that the video and audio tracks of a clip act as a single selection. Linked clips make it easy to keep your media organized and streamline many aspects of editing in the timeline. However, it is easy to accidentally delete more than you intend to. With linked clips, deleting the audio would also remove any video clips that were attached to the selection.

To enable or disable linking in the timeline, toggle the Linked Selection icon which is the middle icon under the timecode display.