About `ModelCheckpoint` starting point
My ModelCheckpoint callback:
ckpt_callback = pl.callbacks.ModelCheckpoint(
    filename="T5-{epoch}-{step}-{val_loss:.2f}-{val_ppl:.2f}",
    monitor="val_loss",
    save_top_k=-1,
    every_n_train_steps=100
)
Questions:

I got the checkpoints starting with 199 step:

Why does NOT pl save the checkpoint in 99 step?
Why is step not an integer multiple of 100? Because counting starts at 0? It is kind of weird.
hey @ShaneTian !

maybe no validation loop is triggered after 99 steps, possibly because total training steps per epoch > 100?
yes, it is zero-indexed.