Line Chart for tracking Market Share

Sure thing, I can provide additional data:

So using the information above, we see that Ghana has a market share of 73.3% (22 machines out of a total 30). 

So when I started tracking this information (August 10th), this is the info that I had to establish the market share. The line chart shows 73.3%, in line with what is in the source excel spreadsheet

Now suppose I find out some new information on August 22nd, and that is the day I update my excel spreadsheet that feeds power BI. Lets say its a new area I didnt know about, and therefore the market share calculation would change:

Now my market share is only 61.1%, once we take in to account the new site. However, when I update the information and refresh power BI, here is what I see:

Instead of a drop from 73.3% to 61.1% market share on August 22nd, I simply see the new calculation in a straight line. I'm hoping to track these changes over time so we can see the rise/fall of market share, so unfortunately this chart is just updating to the most recent market share % with a completely straight line. 

I hope that helps, I dont know what other data you may need, but please let me know if there is anything else and I can provide it.

Thanks!