Mem_size used in kvim2.dts

I was modifying the kvim2.dts to try and change the resolution output and saw meson-fb has mem_size = <0x006AF000 0x01851000 0x00100000>. The comment underneath says uboot logo, fb0/fb1 memory size, so is 0x006AF000 the uboot logo size, 0x01851000 the fb0 size and 0x00100000 the fb1 size?

What would be the maximum sizes available for each of these? For 4K, a lot more memory is needed, so I changed 0x01851000 to a larger value but that would crash the device. Thank you!