Charts from time data not showing properly

One more reply...

If I am correct that your table contains a column of "times" (hours and minutes) that you thought were durations, you can convert them to durations pretty simply.

1. Create a new column temporarily.
2. Assuming your "times" are in column B and are hours and minutes only (no seconds), the formula for the new column will be =DURATION(,,HOUR(B),MINUTE(B))
3. Select all the cells in that new column.
4. Copy
5. Paste Formula Results into the original column (Paste Formula Results is in the Edit menu)
6. Delete the temporary column

Looking at your chart, it appears your data is date&time values. 14:11 is 2:11PM on "day 1". 4:22 is 4:22AM on day 2, which is 14.183 hours later. 18:33 is 6:33 on day 2, which is 14.183 hours later, etc.

Need to see your table to see what you are intending to be tracking and charting. It sounds like you meant to track duration of sleep for each period/day. I don't know if you are entering time to bed and time risen (from which you can calculate duration) or entering what you thought were durations but instead were date & time values. I am guessing you were entering the "time" portion of a date&time value. As such, the "date" part will be assigned by Numbers to be the day you entered the data.

A screenshot of your data, including the sidebar that shows the cell format, might be helpful.

"Odd" numbers on gridlines is kinda normal when the min, max, and steps are automatically set by Numbers. It is not the formatting, it is Numbers making your data fit on the chart all pretty like but with no regard to the "odd" values if puts on the gridlines. Set the min, max, and number of steps to values that make your gridlines come out to numbers you like.