Hi there everyone, I am trying to make standarized graphics with mathematica and I have wroten a code that suits my needs, but I have a littel problem with the thickness of the Legend Box. The legeng box seem fine in mathematica but when I export a PNG with 300 resolution, the legend box is too thick. Can someone tell me how can I change the legendbox tickness and make it work in the export also. Thank You very much in advance for your help.

ListPlot[{UVLED245, UVLED260, UVLED275, UVLED285, UVLED300, UVLED315,
    UVLED325}, PlotRange -> {{220, 355}, {0, 1.1}}, 
  PlotStyle -> "Rainbow",
  PlotLegends -> 
   Placed[LineLegend[{Text@Style["245nm", Opt1], 
      Text@Style["260nm", Opt1], Text@Style["275nm", Opt1], 
      Text@Style["285nm", Opt1], Text@Style["300nm", Opt1], 
      Text@Style["315nm", Opt1], Text@Style["325nm", Opt1]}, 
     LegendFunction -> (Framed[#1, FrameMargins -> 1, 
         RoundingRadius -> 10, FrameStyle -> Directive[Black], 
         Background -> White] & )], {Right, Top}], 
  GridLines -> {Table[i, {i, 220, 350, 15}], 
    Table[j, {j, 0, 1.1, 0.10}]},
  ImageSize -> {800, 600}, AxesOrigin -> {180, 0}, Joined -> True, 
  Filling -> False, InterpolationOrder -> False,
  Mesh -> None, PlotMarkers -> None, PlotRange -> All, Frame -> True,
  FrameTicks -> {LinTicks[220, 350, 15, 4], LinTicks[0, 1.1, 0.10, 4],
     None, None}, FrameTicksStyle -> Directive[Black], 
  BaseStyle -> Directive[Opt3], 
  FrameLabel -> {Style["Wavelength [nm]", FontFamily -> Texto, 
     FontSize -> 22, Black], 
    Style["Absorbance [A]", FontFamily -> Texto, FontSize -> 22, 
     Black]}]