Not Optimized is a new warning in macOS High Sierra. Apple is telling us that in the macOS after the next macOS (Mojave), this app may not run because only 64-bit apps will be allowed.
Optimized, 64-bit versions of Big Business are available now. This Solution provides details. (6775)
Big Business Server for macOS is 64-bit and Optimized for the next, next macOS.
Big Business Client for macOS is available in 64-bit, Optimized for the next, next macOS.
At this time, the recommended Big Business Client for macOS is 32-bit, so is Not Optimized for the next, next macOS, but is optimal for now.
If you are able to run 64-bit Client and give us feedback, that is terrific. The consensus is that its graphics are not fluid but abrupt. And there are some issues with Resources that affect Currencies and display settings.