根据联邦规定，savings acct和money market acct有每个月6次ACH的限制，如果不是在自家银行的ATM上转钱，那么online的transaction里，到checking的transfer也计作6次配额的。估计你的超出四次，很可能是online的转账没有算进去。

可以google “Regulation D"。  原则上记住下面的就可以了：

http://www.moneybluebook.com/be-careful-not-to-exceed-6-ach-transfers-on-your-savings-account-per-month/

Transactions That Count Towards the 6 ACH Transaction Limit Include:

1. Online transfers from savings to a linked account (such as checking)
   
2. Outgoing online transfers made to another bank through ACH or via online wire transfers
   
3. Transfers made via phone banking
   
4. Pre-authorized deductions by a third party
   
5. Checks written from a money market account

However, Transactions That DO NOT Affect Your Limit Include:

1. Transfers and deposits into a savings or money market account
   
2. Withdrawals and transfers made at an ATM machine
   
3. Withdrawals and transfers made in a bank branch via a teller