AM571x EMIF: T_RTW in EMIF_SDRAM_TIMING_1

Hello,

I want to use AM571x with DDR3-1600 memory as 532MHz. What value should I set T_RTW in EMIF_SDRAM_TIMING_1 Register? The parameter value is not listed on DDR3 memory datasheet. Instead, the calculating formula is described in it as below.
RL + tCCD - WL + 2tCK

e.g.) RL=11, tCCD=4tCK, WL=6
11+4-6+2=11
11 minus 1 is not able to set in the field of T_RTW (3-bit width).

I also don't understand how to be calculated the value by EMIF Tool (Excel). Please give me advice.

Regards,
Kazu