According to the datasheet (page 53) the maximum slew rate is 0.7 V/ms between 2.5V (typical Vthreshold switch battery) and 1.8V (power management operating limit). Also according to the datasheet the VDD is 'monitored' every 1 ms.
So the datasheet's maximum slew rate for a typical Vth(sw)bat:
(2.5V-1.8V)/1ms = 0.7 V/ms
However if the Vth(sw)bat is the minimum value (2.1V), see the static characteristics table on page 50:
(2.1V-1.8V)/1ms = 0.3 V/ms
Am I misunderstanding something or is the maximum slew rate actually 0.3 V/ms to cover the full range of part tolerances? Also the slew rate would be measured between 2.1 and 1.8V.
I don't know how your VDD 'monitor' works. I am assuming it works like a sample and hold ADC so you are sampling for a period much shorter than 1ms eg 50us every 1ms.
Tomas Vaverka - it looks like you answered other questions related to this part