Lust for Power bug(?): gains 3 charges instead of max charges

Hi,

I have "Lust for Power" passive in my tree. It says +1 max power charges, so I assume my max power charges is now 4. Another effect is that 5% that instead of 1 charge my character will gain max charges. I use Killing Palm skill with Profusion support to gain charges on culling strike.

My math is as follows:

5%: 4 power charges are gained (5% success Lust for Power)
42.5%: 2 power charges are gained (95% miss Lust for Power + 50% success Profusion)
42.5%: 1 power charge is gained (95% miss Lust for Power + 50% miss Profusion)

However, I sometimes gain 3 charges, but never 4. I am going to allocate more passives for +max power charges, but for now it looks like a bug to me.

Thanks