why does my pivot give me an error?
If you want to show total as your data, then you need to do the following:

select FullName, 
['1-Urgent'], ['2-High'], ['3-Medium (3000)']
from (select FullName,AltBusinessSeverity, total from Mdata) AS ST
PIVOT (
min(total) FOR  AltBusinessSeverity in (['1-Urgent'], ['2-High'], ['3-Medium (3000)'])
) AS PT