This indicates the size of the ROM (Read-Only Memory) or flash storage the firmware is designed for. 4 Megabits (not Megabytes – be careful here) was a standard size for EEPROM chips in the mid-to-late 1990s.
This tells us the architecture (MIPS), the kernel version (2.6.36), and the payload size. Firmware Vst53c-4mb-m.bin
If the image is upside down or mirrored, you can usually fix this in the Factory Menu (Menu + 1147) under "Panel Settings". This indicates the size of the ROM (Read-Only