Custom Drops

You’ll want to trigger the procedure using the trigger in the arrow element for when it hits a mob. Make the procedure check for a cow by using and “If” block and a “Event Target Entity is mob” block in the if block condition. Then, in the if block output, put a repeat block and make the condition an math based “+” block with a “1” in the second slot and round block in the first slot. In the round block, place a “times by” block with a “4” in the second slot and a “random (0,1)” block in the first slot. Place a “Spawn Gem” block in the repeat block output and set the item to spawn to “Milk Bottle” and leave the positions to X, Y and Z.

all if blocks are stored in the "flow control" category

oh, sorry for the delay... but yeah, it's not too easy visualizing procedures or representing them in plain text, especially when some maths are involved, so here I visualized it in the procedure system to save you time! the procedure should look like this:

here's where each one can be found just for convenience:

• Is [event/target entity] (sub)type of [entitytype] - doesn't seem to have a place, so search for "sub" in search bar instead and you will see this in the 2nd result
• repeat [x] times, do [procedure] - Flow Control
• Spawn item/gem [item] at x y z - World Management
• round[value] - Math
• Random[0,1) - Math
• +, -, *, /, and other arithmetic operations - Math