Nope, that 50 blood glucose level is NOT a concern, since Max is not on insulin.
In fact, you WANT to see low bg levels.
Anything between 40-100 is pretty normal for a human glucometer.
I even had a non-diabetic cat that tested in the 30's a couple of times.
That BG of 50 is highlighted in neon green on the SS, because you are using the SS setup for the pet meter, like the Alphatrak. There are formulas behind the scenes, that color code the cells, based on the type of SS you selected and initially set up. That automatic formatting for the color thinks that any number <68 for a pet meter is cause for concern. But no insulin, so you can relax.
Keep testing with the human meter for now, and make a note of that in the Remarks column on the SS, over to the right hand side. If you would be so kind.
Does that help?