Was the -7050 a number that you found by following the directions in the first sketch with your known weight on the scale? If so it isn't an add or subtract, it is a factor that the code divides the measurement by to transform the raw counts into the units of your known weight. The adding and subtracting part of the calibration is done by the scale.tare() line in the sketch.
Without knowing the value of your known weight and its units, along with the weight rating and sensitivity of the load cell, it is hard to say exactly what the -7050 is. But by following those directions you should be able to put units on the -7050. Perhaps the scale factor is something like -7050 HX711_ADC_counts per ounce?
Edit: Ah, I missed the pics. The zeros and the solder joint does indicate that something might be shorted out.