The crew is feeding the Nashorn's PaK 43/1 gun with an 88 mm (3.46 in) projectile.
Armour penetration figures are a bit of a black art and also there are many types of ammo. The 193mm YGG quotes is for a tungsten tipped round which was rare. The standard rouund I have seen quoted at 165mm. Similarly the 17 pdr ABDC round could see off 200mm+ at 1000m but was only about 6% of load out, was less accurate and did less damage on penetration. You pay your money and takes your choice. Suffice to say the long 88mm was an excellent AT gun and capable of taking out any allied tank. It’s crews claimed T34 kills at up to 4000m and it killed one of the only known Pershing losses in the whole war.