#bikinigirl24 appears to be a legend Don... so the old adage of a lower tier member lowering their average playing higher tier member no longer applies, if I understood that correctly.
depending on the game format, skins, match play, stroke play, etc. it may also impact the adjustment to your wgt average.
If it was a stroke play per se, -7 is basically a 29 or a 58 when scored as 18. A 58 alone won't necessarily move your average all that much if you have hundreds of other mediocre rounds in your scoring history as you work towards the 500 ranked rounds to reach saturation.
Since you don't appear saturated, it can have a smaller effect because you are not clearing out any higher scores in addition to posting a lower score. If you were saturated and posted a 58, the odds are you would drop at least .02 or .03 versus .01 because you would have replaced a minimum of 10 strokes and possibly 15 or more so your average could have dropped as much as .03 with saturation. Each .01 is equivalent of 5 strokes once you hit saturation.
Also, since WGT typically rounds up or down, you would be right on the cusp of rounding up versus rounding down. It is why there is usually a margin of error of 5 -10 strokes when someone is trying to figure out how close to saturation they are.
All that being said, sounds normal, but that is a bit how I have come to understand WGT average calculations and effect of saturation.