It would be incorrect to keep Nemeth Code open until the end of that sentence.
Would it be giving the braille reader inaccurate content? No. Would it present a major stumbling block to the braille reader? Likely not.
If a chunk of Nemeth Code material followed after this sentence, it would probably be correct and appropriate to leave Nemeth Code in effect through the single word "or" and the simple, unmodified number 315 so that Nemeth Code could be continued for that theoretical following chunk of Nemeth Code material.
Nonetheless, in the example as it is given, leaving Nemeth Code open would be an inappropriate application of the guidance we have for placement of code switch indicators.