[GAMEPLAY] Dragon's Might buff giving too much AP (& AD?)

The math doesn't work out. I get more than 6% AP if there are any other stat multipliers along with dragon. I've only tried this with AP myself, but I suspect that it also works for AD. I had a friend try to calculate the values for AD, but he went crazy because rounding is inconsistent between every possible place AD is displayed.

Reproduction steps:

1. Have any combination of offensive stat multipliers (pick at least one of the following)

• Put points into the archmage (or warlord?) mastery
• Play any champ with their own stat multiplier (Cassiopeia, Zed?, Riven?, Yi?)
• If AP, buy rabadons deathcap

2. Buy some offensive items and Calculate your stats. Everything is golden
3. Kill dragon to get the first buff stack, Dragon's Might
4. Calculate stats again. The numbers displayed are higher than expected.

Let's look at the first attached picture (numbersyo.jpg).

Magus augment (80 AP) Lich Bane (80 AP) Twin Shadows (80 AP) DFG (120 AP) Zhonya's Hourglass (120 AP) Radoobies Snapcap (120 AP)

80+80+80+120+120+120 = 600

3 points into Archmage mastery (+5% AP) Dragon's Might (+6% AP) Radoobies Snapcap (+30% AP)

600*1.05*1.06*1.3 = 868.14 ≈ 868

Where am I getting that extra 20 AP?

These numbers get even wackier with Cassiopeia since she has her own radoobies passive.

Some things to note about this bug:

• Having the Dragon's Might bonus without any other stat multiplier with produce the expected amounts of stats
• Having any combination of stat multipliers without Dragon's Might will produce the expect amounts of stats
• Having Dragon's Might and any stat multiplier will produce more stats than expected

Now, let's look at the second attachment (nunu280withoutarchmage.jpg). In this comparison, I am using the same rune/mastery setup as the one I've posted in the thread except I have removed the archmage mastery. Note how both builds have the same base AP before multipliers (280 AP). With Dragon's Might alone I get the amount of AP that I'm expecting to get. With Dragon's Might and Radoobies passive I get more than I'm expecting to get.

DFG build (80+80+120)*1.06 = 296.8 ≈ 297

Radoobies (80+80+120)*1.06*1.3 = 385.84 ≈ 386 ≠ 393

Finally, let's look at the third attachment (nunuwitharchmage.jpg). In this comparison, I am using the same rune/mastery setup as the one I've posted in the thread. The left column is without the Dragon's Might buff while the right column is with it. Again, the stats with Dragon's Might remain inconsistent with the math.

Left column (top to bottom) (80+80+80)*1.05 = 252 (80+80+120)*1.05 = 294 (80+80+120)*1.05*1.3 = 382.2 ≈ 382

Right column (top to bottom) (80+80+80)*1.05*1.06 = 267.12 ≈ 267 ≠ 268 (80+80+120)*1.05*1.06 = 311.64 ≈ 312 ≠ 313 (80+80+120)*1.05*1.06*1.3 = 405.132 ≈ 405 ≠ 414

The difference may not seem like much (especially without Radoobies), but a difference exists nonetheless.