"Spirit Soul" ability question, please explain

hi expert players,
i have some new card(s) with this ability "Spirit Soul" but fear that i might misunderstand the gameplay effect mabe, so please explain for how long (duration of that one turn or longer or not?!) does the spirit get an additional Gem symbol? O

OR does the ability only work to increase cost reduction of my Ultimate, in the exact moment when i want to summon my Ultimate from hand, and have this spirit on my field?

example:

[CP14-X07] SKY THE LITTLE PEGASUS {3} -1T
小天馬スカイ (Kotenma Sukai)
Promo X-Rare Topaz Spirit [T] New Age/Imaginary Beast
Level 1 <1>: 3000BP, Level 2 <2>: 4000BP, Level 3 <3>: 5000BP
<Debut Appearance: "X-Rare Plus Six! Super GET! Campaign" (11 January 2014)>

When Summoned (Lv. 1-2-3): You may reveal four cards from the top of your deck. Choose an Ultimate Card from among the cards revealed to add to your hand, then return the remaining cards to the bottom of your deck in any order you wish.
(Lv. 1-2-3): SPIRIT SOUL: Topaz
When you summon an Ultimate to the Field, this Spirit gains an additional Topaz Gem Symbol ("[T]").

Battle Spirits' official Card Ruling FAQs (also posted on the Japanese wiki) should provide the exact answers you're looking for!

Q1.) "I don't quite understand this 'SPIRIT SOUL' ability. What kind of effects does it have?"
If you have a Spirit with "SPIRIT SOUL" effects already on the Field when you are about to summon an Ultimate Card, "SPIRIT SOUL" gives the Spirit in question an extra Symbol of the Gem Symbol specified in the written effects (Ruby, Amethyst, Emerald, Diamond, Topaz, or Sapphire; the Gem Color stated will vary depending on the card) to be used as a potential Core Cost Reducer making it easier to summon your Ultimate.

Q2.) "What happens to the 'SPIRIT SOUL' effect after I summon the Ultimate?"
Once you have successfully summoned an Ultimate creature to the Field, the Spirit with "SPIRIT SOUL" loses the extra Gem Symbol it got from the effect and returns to its normal state.

Thnx, how amazing effect, i must try tohse cards in my first Ultimate deck!!! so i hope to play Ultimate Grand Woden better:-)