[eledmac] multiple LaTeX runs needed

[Marjorie Burghart <marjorie.burghart@xxxxxxxx>]

Dear all, 

I am a reledmac (and LaTeX) newbie, so please forgive my probably very silly questions :) 

When I compile my .tex file with xelatex, I get the following "reledmac reminder" in the log file: 

 The number of the footnotes in this section has changed since the last run.
 You will need to run LaTeX two more times before the footnote placement
 and line numbering in this section are correct.

(the number of necessary runs may vary).

What I do not get is why I see this message even if it is the first time I rum xelatex on this file. 
I would need to know how many latex runs are necessary for each file, because I do on-the-fly a server-side transformations to serve ready-to-read PDFs to the users. 
I've tried running xelatex 3 times on each file, but for one thing it slows down the process, and for another it is not always enough. 

Thanks in advance for your helps! 
Marjorie