version control - Query about mercurial heads diagram and heads counting -

i need understand in of following lines number of heads change. im finding hard understand going on in line 15.. know when repository doesn't have same change-sets when pulling or pushing repository there +1 head.

my diagram looks when tried solve it:

line 12: push clone2 main repository

line 15: push clone2 clone1 (because r3 doesn't similar r1)

line 17: pull r2 & r1 main repository, since r1 , r3 there, i've added r2 .

total heads created: +3

main repository: o--------r2

                   \----r1 

clone 1: o--------r1

             \---r3               \---r2 

clone 2: o------r2---------r3

           \--r1--/ 

the mercurial commands below:

1: /home/user> hg clone http://remoteserver/mainrepository clone1

2: /home/user> hg clone http://remoteserver/mainrepository clone2

3: /home/user> cd clone1

4: /home/user/clone1> echo 1 > a.txt

5: /home/user/clone1> hg add a.txt

6: /home/user/clone1> hg commit -m "added file"

7: /home/user/clone1> cd ../clone2

8: /home/user/clone2> echo 2 > b.txt

9: /home/user/clone2> hg add b.txt

10: /home/user/clone2> hg commit -m "added file"

11: /home/user/clone2> hg pull ../clone1

12: /home/user/clone2> hg push -f

13: /home/user/clone2> hg merge

14: /home/user/clone2> hg commit -m "merged"

15: /home/user/clone2> hg push -f ../clone1

16: /home/user/clone2> cd ../clone1

17: /home/user/clone1> hg pull

while planetmaker's answer in linked question full , valid, i'll note mistakes, omissions , wrong assumptions in this situation

1. clone2 got head+1 on step 11

>hg pull ..\clone1 pulling ..\clone1 searching changes adding changesets adding manifests adding file changes added 1 changesets 1 changes 1 files (+1 heads) 

2. main got head+1 on step 12

>hg push -f pushing z:\main searching changes adding changesets adding manifests adding file changes added 2 changesets 2 changes 2 files (+1 heads) 

http://i.imgur.com/kknu39d.png

3. clone2 got head-1 on step 14
4. clone1 not got head+1 on step 15 (mergeset pushed, previous heads in clone2 parents of mergeset), @ step clone1 equal (in dag-terms) clone2

>hg push -f ..\clone1 pushing ..\clone1 searching changes adding changesets adding manifests adding file changes added 2 changesets 1 changes 1 files 

http://i.imgur.com/9by0urs.png

5. steps 16-17 do nothing, because clone1 dag is fuller main (it has mergeset clone2 on top of main-history)

>hg pull pulling z:\main searching changes no changes found 

6. in order have full history in main must push of clones (-f not needed , useless) have mergeset new single head in repository

>hg push pushing z:\main searching changes adding changesets adding manifests adding file changes added 1 changesets 0 changes 0 files (-1 heads)