http://www.globalsecurity.org/military/world/russia/61.htm
This concerns the 'project 61' Kashin class destroyer aka Rajput class. It has a single quintuple tube 533mm torpedo launcher. As indicated, it carriers 10 torpedoes. That implies 1 full reload on board, and thus some magazine.
The most likely location of such a magazine would be on the same deck lever, immediately behind the launchtable. In Rajput/Kashin/Project 61 that would be below the rear mast that carries the rear SAM fire control radar. I would expect a similar arrangement in the P15 Delhi class, with the mag below the rear search radar mast (between the Barak 1 launchers). It likely that P15 carries at least the same number of reload torps as Project 61.
Since each torpedo would weight sometihing like 1,500–2,500 kg (depending on specific torpedo
http://www.navweaps.com/Weapons/WTRussian_post-WWII.php ), there may well be an assisted loading devices or even automatic loading. This was already employed in e.g. the pre-WW2 Hatsuhara class destroyers of the Japanese
"The later
Hatsuharu class of 1931 further improved the torpedo armament by storing its reload torpedoes close at hand in the superstructure, allowing reloading within 15 minutes."
https://en.wikipedia.org/wiki/Destroyer#Inter-war_.26_World_War_II
"Between the two funnels was the forward 61 centimetres (24 in) triple torpedo tube mount fitted on a low platform. Behind it "was a torpedo locker with its mechanical quick reload system (
Kiryoku sōtenshiki jihatsu sōten sochi) for the three reserve torpedoes inside." To preserve lateral stability the aft funnel was offset to starboard while the torpedo mount was offset to port. The reload locker was also offset slightly to port and angled inboard to facilitate reloading. The middle torpedo mount was positioned behind the aft funnel on the centerline, but its reload locker was positioned identically to that of the forward mount. Superimposed to starboard and overlapping the middle mount was the rear triple torpedo mount positioned on the rear deckhouse. Immediately behind the mount was its locker positioned on the centerline, but angled slightly to the right so that its mount only had to traverse slightly to align with the locker and begin reloading."
https://en.wikipedia.org/wiki/Hatsuharu-class_destroyer
Installation as fitted port and starboard amidship in Talwar/project 11356
The magazine for any reload would likely be below the rear pair of Orekh fire control radars, or between the launchers (with some open space behind it)
This is what you have a pair of in P15A: fixed twin tubes.
As you can see, there are rails of sorts behind each launcher pair. I suspect reloads are moved out from mag(s) into the open transversely and then loaded into the tubes (rather than longitudinally). I see no other way to reloading on these ships.
With Russian 533mm torps having a typical length of 7.5-8.0m and the ship having a beam of 17.6m, it should just be possible (17.6/2=8.8m)