Question about the spiritualist's phantom's damage reduction

[Ziefniel]

Hello,

So, I've been playing a spiritualist for quite some time, but there has always been a question I had in mind about the phantom's DR.

The sentence I have a question about is : "A phantom manifested in ectoplasmic form has DR 5/slashing. When the spiritualist reaches 5th level, the phantom gains DR 5/magic."

This sentence seems to imply that a phantom has a DR 5/slashing, and that upon leveling up it gains a new DR /magic. The thing is, I never saw a monster in the bestiary with two kinds or DR. But, if the phantom only has one kind of DR, it would mean that some weapons that did not damage it(or at least less) at level 1 would damage it at level 5.

Indeed, I believe a magic weapon does not bypass DR slashing, bludgeoning or piercing. So, at level one a magic weapon dealing any kind of damage except slashing would deal less damage to the phantom, but when the phantom reached level 5 it would be damaged by that weapon.

So here comes the question : does the phantom get 2 kinds of DR (slashing and magic), or does it lose its DR/slashing. If so, it would actually mean that the phantom would be a little less "powerful" upon reaching level 5.
Another problem is that the DR eventualy becomes a DR 10/magic, then 15, and finally a DR/-. So the phantom would have two different DR with different values, to finally have only one DR that would apply against all kind of damages.

So here comes the question : what would you rule ?

I personally think that the sentence I quoted implies that the phantom gets to different kinds of DR (the word "has" implies it, well, has the DR/slahing, and the word "gains" implies an addition. If it was the same DR, the correct word would have been "become", or something like this.

Sorry if I made some mistakes, english is not my native language.

[Chess Pwn]

it doesn't say it loses or changes the DR so it has both.

lv1-4 you need a slashing weapon to do full damage
lv5+ you need a magic slashing weapon to do full damage.

[Diego Rossi]

There are plenty of examples of creatures with DR against 2 kind of damage, as an example strong evil outsider often have a DR that require magic and good attacks to be overcome.

Two separates kind of DR are a bit rarer but still fairly common for PC, like Adamantine breastplate plus stoneskin plus righteous might will give you:
DR 2/-
DR 10/adamantine
DR 5/evil or good

In that instance you use the highest applicable DR.

[Ziefniel]

Okay,

Thank you for your answers.