About 20/50, I don't know if that can be unambiguously converted to diopters. I measure by performance by sitting at a constant 20 feet away and when I am over 80% correct I shrink the font on the chart a little bit. I can currently read a slightly smaller font than what corresponds to 20/50 on an eye chart.
So that's fairly minor myopia.
Eye training programs train eye muscles, it's not an issue of fine-tuning "brain software". You can train your eye muscles to compensate, somewhat, but the downside is that if you're e.g. just tired or stressed your vision degrades back to baseline.
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