Thank you for your question.
First, please do ensure that your print is in fact applying bold to certain numbers. Some fonts and/or printing processes can make print appear bold even though it is not.
Information on using bold for numerials is in section 32.b of the Nemeth Code.
The example you give would be transcribed in Nemeth Code as follows:
An example in which one digit of a number than consists of multiple digits is bold would be transcribed in Nemeth Code as follows:
Thank you for your attention and time!