If you are using a Dot Gain, you may need to apply a compensation curve to achieve the desired tones in your separation. 

A typical dot gain curve for screen printing might look something similar to the curve shown below. You can see tones below around 5% will be 0% (not print anything) and above 80% is solid.

This will have the following effect on your tones in a design:

Above this the separation without the dot gain, below is when the dot gain is shown, as you can see it's dark and lacking in contrast. This is what you will get in production if we don't adjust the gamma curve on the layer to compensate for the dot gain effect of production.

To correct this and make the image print in production as we wish (not too dark and flat) we can make a compensation curve for the dot gain.  To this:

1. Go AVA > Settings > Dot Gain and Ctrl click on the curve to show the contextual menu, choose Edit As Text, this will show as below.  Select all the figures and Copy.

2. Select the spot layer or layers you wish to apply the compensation curve to (normally this would be all layers). Go to Edit > Gamma, ^ (control key) click on the curve and choose Edit As Text, select all the text and Paste in the dot gain data, this will give you the original curve (at this point your design will look very dark as the dot gain is effectively being applied twice).

3. We need to reverse the numbers to make our auto compensation gamma curve.  To do this you need to click on each point in the gamma curve and swop around the In and the Out figures.  In the example Below, on the first picture I selected the first node, this comes in at 86% and out at 100%, in the middle picture you can see how the node moves when I swop these around.  The picture of the gamma on the right is after I have swop all the gamma points, i.e this is my compensation curve, you can see it's an inverse of the dot gain.

4. This is quite a complex process, but you only need to do this once.  When you have completed the compensation curve this can be saved as a Gamma or to a Palette ready to be applied to all design.