Median Contract Rent [dollars]: Jam Values & Zero Values

While working with the H056001 variable (Median Contract Rent [dollars]) at the census tract level from Summary File 3 of the 2000 Census, I noticed there are "jam values" in the data of "2000+" and "100-". It is unclear to me whether a jam value of "100-" represents 100 or less or 99 or less. I do see a single tract with a value of 100 in the data, so I expect the jam value of "100-" to represent values of 99 or less. However, there are also values of 0 in the data. Should these values of 0 be treated as missing data/suppressed data? I haven't been able to find clear documentation for these 0 values and what they represent. I am leaning towards the idea that they should be treated as missing given the Universe for this variable is Specified renter-occupied housing units paying cash rent (i.e. a median of $0 for cash rent is not realistic). 

I also looked at the b25058_001 variable (Median Contract Rent [dollars]) at the census tract level from the 2008-2012 5-Year ACS and the 2013-2017 5-Year ACS. In these data there are also jam values of "2000+" and "100-". There are no values of 0, but there are values of "-". I'm assuming a value of "-" means the estimate was unavailable or suppressed?