In the textbook Spacecraft Systems Engineering 4th ed. page 14, table 2.1 ("Acceleration values for the Ariane 5 launch vehicle") provides data on the loading of the Ariane 5 spacecraft. One of the columns listed is "Additional line load" given in units of N/mm. However, the meaning of this field isn't actually described.
Table 2.1 shows the design loads that a satellite must achieve associated with various mission events for the Ariane 5 launch vehicle[...].
Table 2.1: Acceleration values for the Ariane 5 launch vehicle .
No other context is provided to explain or generalize these terms. The table is reproduced as best I can in MathJax, but differs non-critically from print copy.
What is the line load "additional" with respect to (some static load?), and more generally, how should it be interpreted?