Need some insights on 'index_page' variables in Innodb_Metrics Table

I was experimenting with page-split behaviour for sequencial vs random ordered inserts in Mysql,Innodb. For sequencial Inserts I got:

index_page_splits:           3199
index_page_merge_attempts:   0
index_page_merge_successful: 0
index_page_reorg_attempts:   0
index_page_reorg_successful: 0

For random Inserts I got:

index_page_splits:           4423
index_page_merge_attempts:   1
index_page_merge_successful: 1
index_page_reorg_attempts:   1
index_page_reorg_successful: 1

I am having two questions: 1.Why there are increments in **index_page_merge_attempts**,**index_page_merge_successful**, **index_page_reorg_attempts**,**index_page_reorg_successful** variables? 2.What is the difference between **attempts** and **successfull** variables?