10+ is sometimes used as a shorthand for 10 or more. Do not superscript the +.
A superscript + is normally only used for positively charged ions or particles: H+ for hydrogen ions, Na+ for natrium ions, K+ for potassium ions, Zn2+ for zinc ions, H3O+ for hydronium ions, NH4+ for ammonium ions, e+ for positrons,
μ+ for antimuons.
Otherwise, superscripts are used:
- in mathematics, for exponents: 106 is a million, 1 m2 is a squared metre
- for footnotes
- for the abbreviations TM (trade mark) and SM (service mark) following a trade mark or a service mark
- for digits behind the decimal point or comma: $1.50
- for the final letters of ordinals: 1st, 2nd, 3rd, 4th
- for the final letters of abbreviations that contain the first and final letters: Mlle for mademoiselle, Mr for monsieur or mister, Dr for doctor
Modern style guides advise against the use of superscripts in the last three points.