Extending the range of calipers

[mklotz]

Sorry for being a bit thick but what does the ^ mean I've not seen this symbol used before

It stands for "raised to the power". As examples...

x^2 means x-squared
x^3 means x-cubed
x^n means x raised to the n power

In handwritten math the exponent would just be written as superscript. Superscripts and subscripts aren't common on plain keyboards so many programming languages use the circumflex that is on most keyboards to indicate exponentiation.