set_input_delay / set_output_delay -min query

I currently have a query wrt set_input_delay / set_output_delay -min (wrt hold) :

My example below :

#**************************************************************
# Create Clock
#**************************************************************

set PERIOD_CLK 100.000

create_clock -name {clk} -period $PERIOD_CLK -waveform { 0.000 50.000 } [get_ports {in_clk}]

#****************************************************
# Create the associated virtual input clock
#****************************************************
create_clock -name {clk_virt} -period $PERIOD_CLK -waveform { 0.000 50.000 }

#**************************************************************
# Set Output Delay
#**************************************************************
# output_max = [expr $Td_max + $Tsu]
# Tsu is the Max setup time of the external device
# Td_max is the max trace delay of dataout to the external device
set output_max 70.0

# output_min = [expr $Td_min - $Th]
# Th is the Min hold time of the external device
# Td_min is the min trace delay of dataout to the external device
set output_min 50.0

set_output_delay -clock clk_virt \
-max $output_max \
[get_ports flash_nce]

set_output_delay -clock clk_virt \
-min $output_min \
[get_ports flash_nce]

Noticed in many -min input/output delay constraints they use negative values instead of positive ones. Negative values does that mean the hold time after the rising edge of the clock?

I also noticed people using +ve values (see my example above, output_min = +50). With an output_min = -3.0 I had eg flash_addr[5] hold time violations reported worse case -0.569nS (Fast Model)

My understanding is that: output_min = [expr $Td_min - $Th] can be positive or negative depending on the Td_min & Th values. As long as I have the output_min value less than the output_max value, that should be ok. I'm I right to say this ?

Please comment here.

Regards,

Kevin