Okay, this is a very common presentation and like so many others who have fell prey to the voice of the ECG, I'll share with you that the computer hasn't a clue what any of the indicators mentioned actually means. It merely responds to algorithms programmed into it and provides a rudimentary protocol to aid physicians in their evaluation.
Understand that the ECG develops a 3-D pattern of heart function by means of electrical impulses and factors of time related to their travel through the heart muscle. As such, many factors can potentially impose upon the accuracy of the instrument and its readout. Even in the absence of these influences, a premise of mild atrial enlargement would be an incidental finding and unremarkable. It would pose no threat to your heart health in any context.
Remember that in order for the ECG to respond in such a manner, it would perceive enlargement as a delay in signal from one point of the atria to another. Again, this is highly influenced by many factors and in most cases, would constitute an artifact.
Take a breath and relax. The computer doesn't know what it's talking about, it simply responds to pre-programmed data that commonly comes under influence. It confirms the reason that physicians still manage to hold down a job.
Best regards and Good Health