Calculate Symbol-Size From Linker-Map-File

Question

I'm trying to understand linker map files. This is the beginning of my text-section:

.text           0x08000400    0x14ba0
                0x08000400                . = ALIGN (_flash_alignment)
 *(.text)
 .text          0x08000400       0x40 .../lib/gcc/arm-none-eabi/10.3.1/thumb/v7e-m+dp/hard/crtbegin.o
 .text          0x08000440     0x5ee4 .../lib/gcc/arm-none-eabi/10.3.1/../../../../arm-none-eabi/lib/thumb/v7e-m+dp/hard\libstdc++.a(cp-demangle.o)
                0x0800623c                __cxa_demangle
                0x08006300                __gcclibcxx_demangle_callback

I used amap to analyze the map file and it reported a size of 196 bytes for __cxa_demangle and 24096 bytes for __gcclibcxx_demangle_callback.

I thought it works like this:

All the symbols from cp-demangle.o start at address 0x08000440 and there are a total of 0x5ee4 addresses used for all contained symbols. __cxa_demangle starts at address 0x0800623c and ends at 0x08006300 - 1, so it has a size of 196 bytes.

So far, so good - this is matching what amap reported. But how is the size of __gcclibcxx_demangle_callback calculated?

If it starts at 0x8006300 and the whole section for cp-demangle.o ends at 0x08000440 + 0x5ee4 = 0x08006324, then __gcclibcxx_demangle_callback would have a size of 0x08006324 - 0x08006300 = 0x24 bytes. This is far off of the results yielded by amap.

Another thing that I don't understand is: What fills the memory between the start of the section at 0x08000440 and the start of __cxa_demangle at 0x0800623c? At the end of the day, the reported sizes from amap (196 bytes and 24096 bytes) sum up to 24292 which is the same 0x5ee4 (== number of adresses) that is written in the mapfile.