Before and after that period, phone data showed the man organised sales through eight associates.
The illicit enterprise, however, was compromised when the defendant became trapped in Auckland during Level 3 restrictions on August 12.
The restrictions were imposed after four members of one family tested positive for Covid-19 and road blocks were set up around the city to stop unnecessary travel.
Despite the man being unable to leave Auckland, it was not enough to stem the flow of drugs.
"The defendant began sending parcels of methamphetamine to the South Island by courier mail, as he could not return himself," a summary of facts said.
"The defendant sent the parcels to various associates using fake sender names to avoid detection."
The recipients of the P would send money to the dealer by bank transfer, but that too came with risks.
Aware that large sums of cash were piling up against his name, the defendant also directed his customers to use his sister's account.
She would withdraw the money at an ATM or transfer the funds to him.
Between August 2020 and October 2020, 10 packages containing 22.5g of meth were sent to Dunedin and Oamaru, court documents showed.
Two further parcels were intercepted by police.
One, which was sent on August 26, was inspected and found to contain 17g of the drug hidden inside face masks and wrapped in foil.
Bank records accessed by police supported the mounting evidence of drug-dealing.
During the period, the defendant received $40,000 of unexplained cash deposits, and there was about $10,000 of mystery funds in his sister's account.
It was not only class-A drugs in which the man was involved.
Officers intercepted a discussion he had with an associate about cultivating cannabis.
The defendant said he had a heavy vehicle which had been modified with a rear compartment especially for growing the class-C drug.
It simply needed to be connected to a power source, he told his mate.
It was "just sitting there".
Police seized the vehicle in Otago and discovered the set-up exactly as described.
The defendant remains on bail and will be sentenced in the Manukau District Court in August following a successful application to have the case moved north.