"A well-trained force brings peace . . . which brings more time for training!"

Cenn's Tactician

{W}, {T}: Put a +1/+1 counter on target Soldier creature.
Each creature you control with a +1/+1 counter on it can block an additional creature each combat.

Magic Online Promos

"A well-trained force brings peace... which brings more time for training!"

DCI Promos

The choke point was the plan, but devoted camaraderie was always her strategy.

Morningtide

{W}, {T}: Put a +1/+1 counter on target Soldier creature.
Each creature you control with a +1/+1 counter on it can block an additional creature.

The second ability is cumulative. That is, each creature you control with any +1/+1 counters on it can block an additional creature for each Cenn’s Tactician you control. Cenn’s Tactician doesn’t care whether the creature has any +1/+1 counters on it beyond the first.