Hi,
In those situations Conv2d discards the last columns/rows of the input, after padding, as mentioned in PyTorch documentation: Conv2d 56.
In the particular case you are mentioning, that is the same as having a right/bottom padding of 2 instead of 3, as the last column/row is discarded. Translating to the formula that you mentioned to compute the output dimension of the convolution we get (224-7 + 3+2) / 2  + 1 = 112.