Issues with graph display value on hover

[biofio]

I was having an issue with my values on a graph being displayed as a whole number, rather than a decimal as I would like:

Pictured above is the behavior I am talking about, I am dividing, but getting shown a 0, even though the underlying value is clearly a decimal. So I attempted to fix this with FORMAT tool:

 

This was based on previous suggestion in this thread:
https://community.powerbi.com/t5/Desktop/Graph-Hover-Options/m-p/327631#M146252

However, upon researching, FORMAT returns a string and thus that can explain why my graph looks completely broken.

So then, I change it back to what I originally had:

And now suddently everything works how I originally intended. There were no intermediate steps involved: I broke with FORMAT, and then went back (not undo, just delete the FORMAT text in the Measure box), and then the behavior changed.

So two issues:

1. Changing back and forth is changing behavior of unrelated things.
2. Why did my measure display as a whole number in the first place? This is a problem I've experienced elsewhere as well. Sometimes decimals show up as decimals, sometimes as whole numbers, with no real explanation why, or a method to fix it.

[v-qiuyu-msft]

Hi @biofio,

I'm not able to reproduce the issue on my side. Based on my test in Power BI desktop 2.61.5192.601 64-bit (August 2018), as long as the measure format has been set as decimal, the measure values display in chart tooltips are decimal format. 

In your scenario, please ensure the format of measure is decimal. And try to run Power BI desktop in the latest version if possible. Also you can test with our sample report: https://www.dropbox.com/s/uchr1zxw15eh66p/Issues%20with%20graph%20display%20value%20on%20hover.pbix?...

Best Regards,
Qiuyun Yu