13 has special significance in Sikh philosophy. In Punjabi, it is pronounced as “Tera” which sounds the same as “Yours”. Everythings 13, therefore, translates to “Everything is your God”
As a young man working in a shop, Guru Nanak Dev Ji distributed groceries repeatedly saying, Tera. He was saying to the Creator that “This is yours”. Everything we see and we have is given to us by God. Everything is His. We are just a medium to distribute what he has given to share in his Name by remembering Tera. By saying Tera, we remember Guru Nanak and acknowledge this food bank, and everything in it is Tera, His.