Example: $\spadesuit 3.5×10^2$
Here's a screenshot of what shows up for me:
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You are probably missing a font that displays "Miscellaneous Technical" symbols in Unicode. The Wikipedia page has this boxed note in the right hand margin:
This article contains Unicode "Miscellaneous Technical" characters. Without proper rendering support, you may see question marks, boxes, or other symbols instead of "₁₀" (Decimal Exponent Symbol U+23E8 TTF).