Online says TJs plus is 72 percent.
Most unmarked "bittersweet" is somewhere in the 60's. If it's in the 70s, the company will typically take credit for the higher cost.
Let me look at the original recipe and see if you need to adjust. According to Alice Medrich, it's a slight change with butter/sugar.
(I'll be right back.)
Cheezz's idea will also work.