Advance fee payments are payments for services not yet performed; advance expense payments are payments for expenses not yet incurred. Both go into the trust account and may be taken out only once the fee has been earned or the expense has actually been incurred. On each withdrawal the lawyer gives the client written notice stating when, how much and why, together with a complete accounting, sent no later than the day of withdrawal. Whatever the fee agreement says, advance payments stay refundable to the client where the fee goes unearned or the expense is never incurred.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.