CCS/TMS320F28377S: Asymmetrical Deadband even with the same settings

Part Number: TMS320F28377S

Tool/software: Code Composer Studio

Hello,

So I was running the epwm with 1MHz and would like to have the deadband to be roughly 25ns for both rising and falling edge.

So i set the deadband to be 

EPwm1Regs.DBRED = 5;
EPwm1Regs.DBFED = 5;

EPwm1Regs.DBCTL.bit.HALFCYCLE = 1;

I was expecting 25ns for each side but it turns out to be 26ns and 28ns. 

I tried with different values (like 10,10) and yet the 2ns asymmetric still exists. May I know is there a limitation for the accuracy or how can i resolve it?

I read through the manual and I cant find much info about deadband control.

Attached is the measurement from oscilloscope. 

Thanks.