What is an ablatitium?

[Irv Cantor]

I am transcribing an 18th century mathematical text called the E. Knight Arithmetic Manuscript. On one of the pages there is a drawing of a three dimensional rectangular shape, with associated calculations. The very last result of the calculations is labelled "Total or Ablatitium". (I wish I could attach an image of the page.) I was able to find definitions for other terms on the page, like "resolvend" and "parallelepipedes", but I cannot find anything about "ablatitium".
Thanks for any help.