When it hits
From day 14 at 12:00 on the Student's run
Part of 
Zombie Horde - Phase 1, starts with Zombie Horde - Outbreak.
The same wave on the other runs: Wage Slave, Warehouse Manager
Who comes, and where
6 zombies.
Every zombie in it has ×0.98 HP, bites ×5 as hard, on top of the horde setting.
At the door 6
| Zombie | How many | At once | HP each | Bite |
|---|---|---|---|---|
| Office Worker Zombie | 3 | 2 | 127 | 5 |
| Neighbor Zombie | 2 | 1 | 88 | 5 |
| Barefoot Zombie | 1 | 1 | 78 | 5 |
What beating it pays
A wave's total HP sets its reward tier. Each tier pays its reward, and the zombies you kill leave loot on the ground.
| Zombie Horde Intensity | Total HP | Reward |
|---|---|---|
| Weak | 481 | Tier 1 |
| Standarddefault | 641 | Tier 1 |
| Strong | 800 | Tier 1 |
| Very Strong | 960 | Tier 1 |
The game also adjusts each wave to how ready your home is (doors, defenses, supplies and how the last wave went), so the HP here is the starting point.
From the game files1
TowerWave 2002
| ID | 2002 |
|---|---|
| EventID | 52634 |
| OwnerCrisisID | 125 |
| ZombieTypeList | [9103,9101,9107] |
| ZombieCountList | [3,2,1] |
| MaxAliveCount | [2,1,1] |
| ChargeThreshold | 0.2 |
| TargetSlotTypes | [8] |
| AttackMultiplier | 5 |
| HpMultiplier | 0.98 |
| AttackSpeedMultiplier | 1 |
| SpawnAnchor | ZombieSpawn_01 |
| SpawnInterval | 3 |