This extension has numerous accuracy concerns. For example, compare the result of 1/64 on this extension to what your phone says. If you're interested in a better experience, check out my extension: https://addons.mozilla.org/en-US/firefox/addon/address-bar-math/

I haven't added all the constants yet or the saved history but this is otherwise at feature parity and should function better for most use cases. Cheers!