At address 0x8000 to 0xBFFF is flash memory window.
S12DG256 is 16bit MCU, therefore we can directly address only 64kB memory range (0x0000~0xFFFF).
S12DG256 contain 256kB flash, this flash is divided to sixteen 16kB pages (page 30~3F). We can access whole flash trough memory window. At address 0x8000 to 0xBFFF is visible page content according PPAGE register settings. Two pages (3E, 3F) are accessible directly (0x4000~0x7FFF, 0xC000~0xFFFF) and we call them as non-banked.
Default placement for your code is paged flash (banked). Therefore you see your code at page 30.
For details, please check your project *.prm file. Placement of your code you can drive by #pragma commands (for example):
#pragma CODE_SEG NON_BANKED
//your code
#pragma CODE_SEG DEFAULT