Mask Attack irregular running time chunks

[bogesman]

Lets say you run this

Code:

hashcat.bin -O -w 4 -S -a 3 -m 12700 /mnt/d1/hashes.txt -1 ?d ?1?1?1?1?1?1?1?1?1

On the progress line you would see 
Progress.........: 17432576/2186000000000 (there are 2186 hashes in the hashlist)
and on Time.Estimated is (3 hours, 20 mins; Runtime limited: 50 secs)

Code:

hashcat.bin -O -w 4 -a 3 -m 12700 --keyspace -1 ?d ?1?1?1?1?1?1?1?1?1

response is
100000000 which is correct

1. So question one is how comes 2186000000000 which is not  2186*100000000. It has extra 0.

now if you try to chunk this like this
first half

Code:

hashcat.bin -O -w 4 -l 50000000 -S -a 3 -m 12700 /mnt/d1/hashes.txt -1 ?d ?1?1?1?1?1?1?1?1?1

second half

Code:

hashcat.bin -O -w 4 -s 50000000 -S -a 3 -m 12700 /mnt/d1/hashes.txt -1 ?d ?1?1?1?1?1?1?1?1?1

2. Is this chunking correct or what other values should be used?
3. There must be something wrong because, the estimated time for first half is 20 mins and for the second half is the rest of that total time or 3 hours. Why is that and how to properly do even chunks?