If you check that option and selected 20, it will login the first 20 accounts in the list. And when they or one of them logged in succesfully and started posting, it will login other accounts. It will not wait for the first 20 accounts to finish posting before starting other accounts, it will just wait for the login process to complete before starting on other accounts.
Suggestion for improving this feature: As a hypothetical, if we are using a 1:4 ratio, proxy:accounts, to avoid Twitter flagging our proxies, I think it would help to have that function -- the log on limitation -- actually limit logon to a user defined number of accounts (20 in my example above), rather than logging on to ALL accounts in increments of 20 without any limitation of activity on those accounts and proxies. Log on is stepped, but activity is not. After the Tweet Poster module has logged onto the accounts in a list, posting activity on all accounts is simultaneous and this is bad.
Example: As it is now, if the user sets "login account" number to 20 and is using 20 unique proxies for 80 accounts (4 accounts per proxy), TA will log onto all 80 accounts in 20 account increments and start posting activity on all 80 accounts. This leaves each proxy more vulnerable (higher risk of being blacklisted by Twitter). As the number of accounts is increased, the problem is compounded.
In other words, in this example, the Tweet Poster module currently logs on to all accounts in increments of 20, but does not limit posting activity to 20 accounts: after TA log on is completed in increments of 20, there is simultaneous activity on all 80 accounts.
Improvement: Instead, have TA stop at (1) a user defined number and pause for (2) a user determined period of time before logging onto the next set of 20 accounts in the list. This would allow us to stagger account activity, as well as account logon.
This way, the set of proxies used is not exhausted (flagged as suspicious) by Twitter from simultaneous, repetitive activity on that set of proxies.
This would also allow us to perform simple tweet post tasks without having to generate schedules in the text files.
Unless a user has a 1:1 proxy:account ratio, the current Tweet Poster module configuration will quickly exhaust those proxies, resulting in Twitter blacklisting them.
Note: To all people thinking of buying TA/AC, I think they are kickass programs. Just trying to improve upon a good design.