Number of steps per epoch don't match number of batchs in train loader
🐛 Bug
When using trainer, the number of steps don't match the number of batch in the train loader.
For example, when using the Boring model, we have 313 batches in the train dataloader, however, when training we get 626 train steps according to the progress bar.
Furthermore, when using the val_check_interval parameter in the trainer we get totally different results.
For val_check_interval = 10 we get 10016 steps, val_check_interval =50 we get 2191 steps and val_check_interval =100 we get 1252 steps
To Reproduce
Use following BoringModel
Expected behavior
We expect number of steps to match dataloader length
Environment

CUDA:

GPU:

Tesla T4


available:         True
version:           10.1


Packages:

numpy:             1.19.5
pyTorch_debug:     False
pyTorch_version:   1.8.0+cu101
pytorch-lightning: 1.2.5
tqdm:              4.41.1


System:

OS:                Linux
architecture:

64bit



processor:         x86_64
python:            3.7.10
version:           #1 SMP Thu Jul 23 08:00:38 PDT 2020