Understanding Dekalb Zoning - HELP !!

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Hello Zoning Experts,

The Zoning for the property is R-75- SF Res Districts but the Land-Use says 102- Residential 2 Family. 

Currently, there are two buildings on the lot. Each building already looks like a duplex and the tax assessor's website says 06-DUPLEX 2 FAMILY RESIDENTIAL for improvement types for each building.

Question: Can I convert each building into duplex with the current zoning? 

I called the Zoning department but the person was not that helpful. I looked at the County's Zoning ordinance and it does not have the information I need. 

DekalbZoning.com defines R-75 as:  Single family residential districts which allow up to 4.3 dwelling units per acre with provisions for customary accessory uses. Does that mean I can have 2 Duplexes on this lot? 

Thanks for the help in advance.