Conjunction is a word that connect words, phrases, or clauses. The conjunction understand++ is a conjunction in ASL. It is not literally "understand" in English meaning, not at all. Just for the sake of glossing a similar sign. It somehow connotates along the line of "however...", "unless...".
Gloss: "understand++" as a conjunction.
Like other conjunctions, UNDERSTAND-conj is accompanied with raised eyebrows and the movement is twice or sometimes trice. (a gloss symbol /\ for raised eyebrows).
English translation with an ASL gloss for the conjunction: Okay, I can loan you this book, /\understand++/\ I need it back by next Monday for class.
Glosses: #ok, fine++, ix-me can loan-you, /\understand++, book/\ must (you)#back(me) future[cs] monday
Also see conjunction FINISH