Automint - The PIVX wallet is set to convert 10% of the wallets available PIV to zPIV automatically. This can be adjusted in the GUI within the Options dialog, which allows the preferred % to be adjusted as well as the ability to set the preferred zPIV denomination that will be minted. Automint is set to be triggered when additional blocks are added to the block chain and is programmed not to convert your coins all at once.
Automint can be disabled by adding enablezeromint=0 to the wallet configuration file. The preferred mint % and denomination can also be set by the configuration file using zeromintpercentage=<n> and preferredDenom=<n>.