In a journal, the following statement is a condition for submitting a paper. Does this statement mean that I must pay in order to publish my paper? If not, what is its meaning?
If desired, 25 free offprints of the article will be sent to the corresponding author. Additional offprints can be ordered when sending the proof corrections. The article can also be published in Open Access (that is, with the final print file also freely downloadable) upon paying a fee of 300 euros. The decision should be communicated at the proof stage; the appropriate invoice will then be sent to the author.
If it is possible, please clarify the meaning.