According to some sources the ship in its period around 1942-1944 was holding 240 mines. Cannot find sources about depth charges.

1931: 2x 8,35cm/L 55-Flak Skoda, 4x 4cm /L67 Flak , 1 Kran 6,5, 1 Bordflugzeug DH 60-Moth.
1937: + 100 Minen.
1941: + 2x 2cm Flak, 1x 1,5 cm Flak, 6 Wabo-lager (12 Wabos), U-Boot Horchgerät.
1942: 2x 10,5cm, 5x 3,7cm, 6x 2cm Flak, 240 Minen
1944: 2x 8,8cm, 5x 3,7cm, 13x 2cm, 240 Minen

If someone has links about that I would be glad if you can share them.

Presumably Gaijin based Drache on this drawing of it from Warship International’s 2001 article on Zmaj/Drache

Along with this image from the J. L. Roba collection featured in the same article

Interestingly as you can see the 88mm is different

While in-game Gaijin just copy-pasted the SMS Helgoland’s low angle 88mm mount. Presumably to save development time.

As for the mine number, Gaijin just chooses some arbitrary smaller number because you are never going to use 240 mines. For example HMS Abdiel can carry over 100 but it only gets 40 in-game.

Use of mines in WT is even more removed from reality than other combat mechanisms, so only allowing a small-ish number of mines on board makes sense … to me at least.