when talking about a 10 man-month project... do you rather think of 10 man x
1 month or 10 month x 1 man ?

An operational point of view is to think of the size of a staff (say 4) and
then divide ... Then 10 man-month is a shortcut for (10/4) month for a staff
.... when no parallelism, no reuse can be done beetween the two parts of the
job...

Xavier