I have a feature class I am trying to symbolize using graduated colors. The data is grouped by manual interval using "year" field to show when a lot was developed. When I turn off the "show values out of range" option about half of the features disappear. There are no null values in the dataset.
I know this is old but I ran into a similar problem and came across this trying to find an answer. Since there wasn't an answer and I believe I found my own I figured I'd help out the next person who came along. There may be a better way to fix this but this is what I stumbled upon.
In the symbology pane if you choose the Histogram tab instead of Classes there are numbers at the top and bottom of the color bar. Those seem to be setting the out of range limits. You can just click on them and edit them manually. In my case the lower limit needed to be changed to 0 instead of its preset value which was causing some of my data to be "out of range."
I have a similar problem in Pro 2.9.2.
The field I am using in the symbology is from a joined table - I thought that might have been causing the issue, but I have tried using another field from the feature class itself - area - and it still doesn't show up unless I show "out of range" values. I tried the other advice here about the histogram and that didn't work for me either.
For me this is for a PDF map series, so the workaround if I don't want "out of range" in the legend will to replace the legend with a manually adjusted graphic. I have logged this with ESRI support also.
manual classes was also suggested.
A case number would be useful for others wanting to follow the status of the issue