The column EXCLUSIVE_ALLOCATED_SIZE in monitoring view M_HEAP_MEMORY (respectively HOST_HEAP_ALLOCATORS) contains the sum of all allocations in this heap allocator since the last startup. Normally also a lot of deallocations happen, so the EXCLUSIVE_ALLOCATED_SIZE can be much higher than the currently allocated size.
For example, if over time 100 MB are allocated and deallocated 10 times, the actual allocated size is 0, but EXCLUSIVE_ALLOCATED_SIZE would show 1 GB (10 * 100 MB).
If the overall allocated memory is much higher than the overall used memory, the difference is usually free for reuse, so no longer heap allocator specific. Therefore the EXCLUSIVE_ALLOCATED_SIZE information can only be used to understand which heap allocators have the highest "throughput" in terms of memory allocations, but it is not helpful to understand the current memory situation.