Most #AWS instruments have two amplitude (attenuation) settings: collars and liquid. This is analogous to a volume control, the collar setting is turned up listening for quiet reflections while the liquid setting is turned down listening for a loud reflection (i.e. the entire sound wave returning). Some instruments run the two side-by-side on the same wide paper chart. If you have the single paper strip chart be sure to conduct shots using both settings and line them up for accurate and definitive interpretation.
Adjust the amplitude on a paper chart instrument so the pen does not strike the edges. Even worse is the pen striking and sticking to the edge—the amplitude is too high!