Some bug about Pain Attunement or Spell echo or GMP

"

Vipermagi wrote:

Strength grants Increased Melee Physical Damage - it does not apply to Spectral Throw by default.

Anyways. -62% mult and -30% mult works out as follows:
Calculate total %reduction, calculate total flat reduction, subtract.
(100 + -62) * (100 + -30) / 100 - 100 = -73 (*)

29 * 0.73 = 21.17, rounds to 21
29 - 21 = 8

54 * 0.73 = 39.42, rounds to 39
54 - 39 = 15


* = To my recollection, this is the only place PoE does not round down, but to nearest instead.

Tried this approach but it throws off lot of other test builds.
Example of just main hand of dual wielded Dual Strike + Melee Physical Damage gem build:

Main Hand Physical Damage: 24 - 95
82% increases applied: 43.68 - 172.9
-- more/less multipliers:
Dual Strike (Deals 90% of Base Damage)
Dual wielding bonus (20% more Physical Attack damage)
Melee Physical Damage support gem (30% more Melee Physical damage)
-- Total rounded multiplier: 40%
Main Hand Physical Damage: 60.68 - 241.9 (In-game displayed damage range: 61 - 243)

So, it looks like there is something else goin on.

@chris_ov
In your case, Vipermagi's system of precision loss with multiple multipliers works.

Base Fire Damage: 358 - 537
% increases: * 6.2 = 2219.6 - 3329.4
% more/less: * (0.5 * 0.9 * 1.3)
=> RoundX(0.585, 2) // 2 digit precision
=> * 0.58 = 1287.368 - 1931.052

RoundX can be Round half down (10.5 => 10, 10.51 => 11, 11.5 => 11),
or Round half down after even digit (10.5 => 10, 10.51 => 11, 11.5 => 12)
but it can't be truncatenation, because it would break my ST-Fork calculation :)

@Vipermagi
I have feeling that there is different formula for spells and attacks (or even dual wielding?) in a sense of rounding.