What's the deal with minimum interest charge?

[IWOL]

I have seen on a few of my cards a minimum interest charge of $2 and I don't understand what that is.

My Arrival Plus is at 0% till Feb of 2015. I paid the balance to 0 before statement cut and the statement posted with a $2 balance.

it shows as minimum interest charge. I used my Barclay card this month to fund my new DCU savings and membership which was a $5 and $15 charge that Baraclay categorized as a cash advance. They charged me $10 cash advance fee on each of those charges. 

I called them about it and they gave me credit for both charges but warned that any charge from a financial institution would be coded as a cash advance.

is the $2 min charge related to that?

Don't care that much about the $2 charge but trying to get all cards except one to report 0 balance just so I can see my max score under current profile but it's harder to do than I thought.

[Suddenlyy]

in addition to the cash advance fee, they also charge interest on those amounts starting on the transaction date. so by the time your statement cut, a small amount of interest had accrued from those cash advances. suppose the interest that accrued was just 15 cents, they wont bill you just 15 cents of interest, they will bill you the minimum interest charge, which apparently for your card is $2