For example one or more of the following: turnover, number of employees, total transactions, prior year audit fee, etc
Give the auditors an idea of the audit fee you expect. (EG <$1,000, or, last year was $2,500, or, around $5,000, or, not more than $750).
NOTE: if you put this unrealistically low then less auditors will be interested in your job, reducing the likelihood of you getting the best auditor for you.