How to write and publish a scientific paper - Barbara Gastel, Robert A. Day 2022

Exponents in table headings
How to design effective tables
Preparing the tables and figures

If possible, avoid using exponents in table headings. Confusion has resulted because some journals use positive exponents and some use negative exponents to mean the same thing. For example, some have used “cpm × 103” to refer to thousands of counts per minute, whereas others have used “cpm × 10−3” for the same thousands of counts. If it is not possible to avoid such labels in table headings (or in figures), it may be worthwhile to state in a footnote (or in the figure legend), in words that eliminate the ambiguity, what convention is being used.