Add Lines to Chart

Hey Everyone!

I have a concentration reading chart for some soapy water that has to be measured and fall within a certain range.

I have the chart pretty much made, but I cant seem to get the baseline to show me 17%.
The manufacturer recommended concentration is between 17-20% and the previous chart I made in 2015 I somehow figured out how to add yellow lines to the graph to indicate this. I included a scanned copy on tab 2 for reference.

Thanks for any help! and any recommendations to make this better I'll gladly accept this isn't my area of expertise clearly since the last time this chart was made was almost 5 years ago.

Thank you, Got them added!

One more question about this chart.

I'm trying to change the axis's and it completely ruins the whole chart. I'm thinking it has more to do with how I have the data laid out for the chart to use?