Hi,
The styles works for "borderTopStyle" and "borderBottomStyle" are
"none" | <All predefined border style names>.
Here are Predefined border style names:
"dash dot", "dash dot dot", "dashed", "dotted", "double", "hair", "medium dash dot", "medium dash dot dot", "medium dashed", "medium", "slant dash dot",
"thick", "thin"
There is no "Dotted Thin" style in the Predefined border style names. And as far as I tested it works well for me. You can check whether the code works by right clicking the cell:

You can get more detail about data fromating form link below:
How to: Format tables in apps for Excel
Best regards
Fei
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