When Diamond weapon blocks, Arena client does not allow to distribute trample damage, if any damage was dealt to it. Encountered this in situation described in “WTR” section and because of this I've lost my draft while having lethal. I should've dealt 8 damage to an opponent while they had 6 life and it cost me the game. Please compensate me a couple of hundred gems I've lost because of this.

WTR
1. Start turn with Diamond Weapon in the play, Light of Judgmen in hand and at least 10 lands, including at least 1 red source. Opponen has an untapped Diamond Weapon as well
2. Equip it with Samurai's Katana.
3. Attack with it.
4. Opponent blocks with Diamond Weapon
5. Cast Light of Judgement targeting opponent's Diamond Weapon
6. Go to Combat Damage step

Expected Result: interface must allow you to deal at least 2 damage to blocker and up to 8 damage to an opponent.
Actual Result: interface dose not allow to deal less than 8 damage to blocker

According to rules:
702.19b The controller of an attacking creature with trample first assigns damage to the creature(s) blocking it. Once all those blocking creatures are assigned lethal damage, any excess damage is assigned as its controller chooses among those blocking creatures and the player, planeswalker, or battle the creature is attacking. When checking for assigned lethal damage, take into account damage already marked on the creature and damage from other creatures that's being assigned during the same combat damage step, but not any abilities or effects that might change the amount of damage that's actually dealt. The attacking creature's controller need not assign lethal damage to all those blocking creatures but in that case can't assign any damage to the player or planeswalker it's attacking.