Map mod calculations

Hi all. Up front, I was never good at math and do not really understand how poe implements a certain map mod...I was hoping to get some help from you all.

Basically, I modded a map which included a mod which reduced the players maximum resistances by-10. I didn't feel this was that big of deal. I had some of my resistances way over cap. When I landed in the map, the numbers were way off from what I was expecting. My simple brain figured they map would reduce my resistances by 10...at least that's what the map mod said....but in fact, it was something completely different. I've included links to screen shots for before and after and was hoping for some feedback on what I missed here.

My initial defenses, as listed in the defense tab within my hideout where...
Fire 75(194)
Cold 75(92)
Lightning 75 (147)
Chaos 75 (75)

After I landed inside the map, the defense tab said...
Fire 65(134)
Cold 32(32)
Lightning 65(87)
Chaos 15(15)

Please explain the math...how is that -10 to player maximum resists

Screen shot before
http://imgur.com/a/Vmm5i

Screen shot after entering zone
http://imgur.com/j3GjLWw

What am I missing? Elemental weakness is looking like a far better anti-player mod.

Merciless difficulty has -60% resistance penalty while your hideout is in normal difficulty. That is the reason for 60% drop across the board. Your cold resistance is not capped in merciless even without map mods that penalize it further.

To show it in numbers.

These while in hideout. Normal Difficulty. No negative resistances to start.
Fire 75(194)
Cold 75(92)
Lightning 75 (147)
Chaos 75 (75)

These while in zone. Merciless Difficulty.
-60 resistances to start.
-10 to maximum resistances (due to map mod).

Note: 75 is the default maximum elemental resistances allowed.
The mod on the map gives -10 to Maximum resistances, not to your resistance values.

-> Overall resistance -60. Max resistance capped at 65.
-> (Unless max resistances are modified in some way. (passives/armor/flasks/aura/et cetera))

Fire 75(194) -> 194 - 60 = 134.
This is above the resistance cap of 65. Resistance capped at 65.
-> New Fire 65(134)

Cold 75(92) -> 92 - 60 = 32.
This is below the resistance cap of 65. Resistance stays at 32.
-> New Cold 32(32)

Lightning 75(147) -> 147 - 60 = 87.
This is above the resistance cap of 65. Resistance capped at 65.
-> New Lightning 65(87)

Chaos 75(75) -> 75 - 60 = 15.
This is below the resistance cap of 65. Resistance stays at 15.
-> New Chaos 15(15)

Tldr,

Hideout is normal difficulty with no resistance penalty. Merciless has -60 resistance and the map has -10 to your max leaving cap at 65.