I really not sure your point. Does acts tell you that God requires you to give 10% of your income?
Your church sounds like an outlier. Many of the church I've seen have been seeded by larger churches and ministries which they are then indebted to. Most of which would not be so forthcoming with their financials.
Thats not the question though. Why is it a church would say that tithing 10% of your income is a requirement?