Thank you for the response!
I checked the input values after reading your comment, and it seems the values were not precise enough. For example, I changed the point
-157.65, 21.3
to
-157.654198, 21.297908
and the second, newer value input is closer to what I want. So it seems I needed to be more precise with my inputs.
The point is still a little off however. In the attached picture, the more precise input value appears as the peach dot. But in Google Maps (GM), the same coordinate value appears where the red dot is. Using AGOL's measurement tool, the longitude value for the red dot in AGOL is -157.654135. Do you think this difference is simply that the basemap may be a little off from GM? Admittedly, now that I've fixed the input values, the difference is incredibly minor. But I was curious if this is problem with transferring GM long/lat measurement into AGOL, or simply a matter of me needing to adjust the dot manually given it is already so close to what I wanted, or something else.