Quoted from BW1029:See the attached as an example. I haven't touched any of the legs and don't have an accurate way to measure slope, but the leveler bubble shows right in the middle where I believe its supposed to be.
[quoted image]
Yep, that's just too flat.
So regarding that bubble level on the right side built into the playfield: Unfortunately I've seen them differ when the bubble is in the middle for up to 0.5* from machine to machine of the same type.
I bought something like this https://smile.amazon.com/gp/product/B00WQLHG2G
That will help you easily make the machine level from side to side and determine your slope front to back. I'm sure you can find them cheaper than that, they are all likely rolling out of the same factory in china. Wouldn't be surprised if you find one for $15 or less.
In the meantime:
Just let some more of the leg leveler out in the back even if the bubble will wander up. (Don't forget to also move the jam nut underneath up so the machine is sitting on the nut and not just the threads.)
Once you have your new little device you can verify what the incline is in degrees and also make sure its level from side to side. I found also out the hard way that this little bubble thing on the right side is not really useful.
Edit:
Reminder if you use that little electronic inclinometer, always measure on the playfield, never on the glass!