Is it showing 0.0a with no tank on it?

If so what you may have probably done is overtightened your tank and smashed the the o-ring under the firing pin on your SVD. This make's it ground out. You may be able to fix it by resetting the o-ring/bushing under the firing pin with a small screw driver by lifting firing pin up slightly and pushing the rubber bushing back under pin. If you have ruined this bushing there is another way to fix it.

Here is a video link that shows you how. Don't worry that it is showing a vamo as the fix will work on most any device showing 0.0a

How to fix low 0.0a low click here