Hey Alexa,

Several possible explanations for this.

Some institutions aren't really authorized to obtain foreign work permits themselves, so they form an alliance with (read: pay a bribe to) an institution that is. This other institution may not necessarily have permits earmarked for teachers.

Other places get X number of work permits per year, divvied over several different occupational areas. They tend to just grab whatever's available.

Bottom line: means nothing to you personally. All that matters is that you have the work and residence permits held tightly in your kung fu grip.