I say it was a vaccine of some sort. Notice the Quarantine written on the hatch was on the INSIDE. He's protecting himself from something on the island.
Also, the numbers were on the label of the Vaccine.
See Here
I checked this out for myself on my downloaded episode and it's legit.
I am intrigued by the interior of the hatch as far as a time line. He has a lot of old stuff, but he also has a brand new washer and dryer and other things....