In the closing scene max looks at his phone and it says Wednesday 21st February but earlier in the programme he looks at it to see it says, Saturday 18th. February (the murder is mentioned as happening on Friday 17th). Saturday til Wednesday is 4 days. 18 - 21 is only 3.
When the two police detectives search the storage unit, they use flashlights. Every storage facility has ample lighting to accommodate their customers in the unit; no need for flashlights.