Being Sued by Tenant

[A.R Shakir]

My tenant in Chicago send a claim from a lawyer, stating I owe 27 thousand dollars in damages for not returning the complete security deposit.  The security deposit was 10 thousand dollars, she did not pay the last months rent, so 6550 was left. I charged 2,600 for repairs and damages, and sent receipts and pictures. I did not return the money from where the account is being held, and I did not return interest. It was an oversight from my part, but for 2600 I being sued for 27 thousand.....

Any way to approach this.?