the target symbol means "used for or graphically interchangeable with the following (may be followed by more than one other graph)". The line "MC tawX" is the Middle Chinese reconstructed pronunciation. As to why there are no Old Chinese pronunciations, it says,
"Why, one may ask, are only the Middle Chinese readings supplied in the dictionary, and not the Old Chinese readings too? The simple answer is that there is a relatively stable consensus about Middle Chinese readings (though specialists argue about certain points of detail), whereas the linguistic reconstruction of Old Chinese continues to generate broad dispute and widely divergent representational models. Moreover, Old Chinese itself is in large part a back-projection from the established phonological values of Middle Chinese and is thus largely an abstract outgrowth (or perhaps we might say pre-growth) of it. Given the relative certainty of Middle Chinese reconstruction and the relative uncertainty of Old Chinese, it has therefore seemed the safest course in a dictionary meant for general use to provide only the Middle Chinese readings for words. Of the several systems for Middle Chinese reconstructions that have been proposed over the years, that of William Baxter and Laurent Sagart enjoys the widest acceptance among scholars. For the MC readings in this dictionary I make use of the Baxter-Sagart reconstructions as given in their online posting of 20 February 2011. Any errors in the reconstruction of words included in the dictionary but not in their 2011 list are entirely my fault."