From an ex-armoured car guard who worked on bank machines for 15 years, unless things have changed, a bundle is 100 used bills rubber banded or wrapped with a paper band. Normally used bricks were made up of 10 bundles rubber banded together. Sometimes they were shrink wrapped. A new brick is 1000 new bills tied with flat plastic bands and a new block is 4000 new bills tied with flat plastic bands and wrapped in plastic with a sticker on the end listing enclosed serial numbers. On one occasion I had a block split and banded in two halves and banded together as 1000. The one 500 bill half was sequential replacement notes. Replacement notes were very common. I never did find any error bills or experimental bills.
$5 block $20000
$10 block $40000
$20 block $80000