What the max size of "Text" in motoko

During my testing
i call my canister with a size about 2mb. the canister will cause error.
and i got something like “ic0.msg_reply_data_append: application payload size (2621575) cannot be larger than 2097152”

2097152 is equal to 2mb

and i found MAX_INTER_CANISTER_PAYLOAD_IN_BYTES and some variables like max_reply_size here

it seems limited to 2mb rather than 2GB.

can someone explain about those variables.