In case further clarification is needed, this from Rob Hyndman, author of
the Forecast package, may be helpful:
"fitted produces one-step in-sample (i.e., training data) "forecasts". That
is, it gives a forecast of observation t using observations up to time t-1
for each t in the data. ... So fitted(fit) gives one-step forecasts of
observations 1, 2, ... It is possible to produce a "forecast" for
observation 1 as a forecast is simply the expected value of that
observation given the model and any preceding history."