// <decimalSI>       ::= m | "" | k | M | G | T | P | E
//
// 	(Note that 1024 = 1Ki but 1000 = 1k; I didn't choose the capitalization.)
//
// <decimalExponent> ::= "e" <signedNumber> | "E" <signedNumber>
// ```
//
// No matter which of the three exponent forms is used, no quantity may represent
// a number greater than 2^63-1 in magnitude, nor may it have more than 3 decimal
// places. Numbers larger or more precise will be capped or rounded up.