Yup, I totally meant to say $11,000! Thanks for catching that,.
And if I understand the question you are asking at the end, yes, that is exactly how the LexisNexis Auto score treats ACL. Here are a series of reason codes for it (code 3030-3038):
3030 Average Credit Line on Bank Revolving Accounts is $725 or Less
3031 Average Credit Line on Bank Revolving Accounts is $726 to $1,024
3032 Average Credit Line on Bank Revolving Accounts is $1,025 to $2,075
3033 Average Credit Line on Bank Revolving Accounts is $2,076 to $3,109
3034 Average Credit Line on Bank Revolving Accounts is $3,110 to $4,778
3035 Average Credit Line on Bank Revolving Accounts is $4,779 to $5,773
3036 Average Credit Line on Bank Revolving Accounts is $5,774 to $6,175
3037 Average Credit Line on Bank Revolving Accounts is $6,176 to $7,919
3038 Average Credit Line on Bank Revolving Accounts is $7,920 to $10,532
As you see, when your ACL exceeds $10,532 there is no longer a penalty (in the LN system).
To circle back to your own particular situation, since the difference between your oldest open account and your second oldest open account is so small, then all that will happen (ten years from now) when the account you are about to close falls off is that your Age of Oldest Account will drop by nine months, which will not be a big deal.
Finally, to answer the other question you ask, "Age of Oldest Account" is computed by looking at your oldest account -- closed or open. This is why closing it now will have no effect on the "Age of Oldest Account" factor for roughly ten years -- not until it falls off.
