ADXL213 complete cycle error

Hi ADI team. My customer use ADXL213 for pipe inclination sensor. ADXL213 output PWM data and be able to set the period for a complete cycle to set a single register. In Data Sheet, "t2 = RSET/125 MΩ" is described. But, when my customer set 1MΩ register, t2 become 8.6ms.  in spite of the theoretically, t2 become 8ms. my customer check a register, but the register is no problem. We suspect internal register's error. Please teach us the internal register error value.