Position line is offset of the actual position?

I know that looks a little weird, but it is actually correct.

The dots that you see when you zoom in close are the “samples”.
Samples occur at evenly spaced intervals, according to the “sample rate”. For example, if the sample rate is 44100 Hz (44100 samples per second), then the distance between each sample (the “sample period”) is 1/44100 = 0.000022676 seconds.

Imagine if you had an extremely short audio track that had just one sample. The sample period is 0.000022676 seconds, so the effective length of the audio track is 0.000022676 seconds. In digital audio, “one sample period” is the smallest unit of time - all durations are “quantized” to exact multiples of the sample period.

Now, if you zoom in at the very start of an Audacity track, you will see that the first sample is at time = 0.0000 and the second sample is at 0.000022676 (OK so you can’t actually see with that much precision, but I hope you are following my drift).
So each sample represents a time range that starts from the “dot” and goes up to where the next dot will be. Thus, if the final sample of the track is selected, the time period covered by that final dot extends to 0.000022676 seconds after the dot.

Does that make sense now?