Dear Roya,
reading the whole sentence in the manual (sec.2.4 tutorial.tcl) answers your question:
Note that the electrostatic interaction is only activated after equilibrating the excluded volume interactions, which speeds up the warmup phase. However, depending on the problem, this split warmup may not be possible due to physical restrictions. ESPResSo cannot detect these mistakes and it is your responsibility to find simulation procedure suitable to your specific problem.
It is _usually_ better but not necessary to put Coulomb after the warmup. The warmup is intended to quickly get rid of unphysical overlaps due to short range interactions. If you activate Coulomb before the warmup, it becomes much slower but should not do any harm.