://ark.intel/products/72164/Intel-Core-i5-3230M-Processor-3M-Cache-up-to-3_20-GHz-rPGA
2 cores, 4 threads - maybe right click on your graph in your performance monitor and switch to the logical view.
p.s if you want unreal to use 99%, build a dedicated server or android client - press F to pay respects to your CPU 
p.p.s also in the editor settings there is a “use less cpu if in background” setting in miscellaneous - maybe uncheck that as technically if you are using your task manager, its in the background