When the Channel IE type is set as "timeslot" , this specifies the B channel to use for a call as a number. For example, if a Q931 message such as a Restart message refers to B channel 5, the channel IE contains the number 5.

If it is set as "Use number when 1B" , it will specify the B channel to use as a timeslot (discrete number) for any message that refers to a single B channel, but it will summarise all the timeslots as a bit mask to represent all the channels if the mesage refers to multiple B channels.

This bit mask summary is also refered to as a "Slotmap".

Only certain messages (such as Restart) can specify a range of B channels. Normal call control (Setup/disconnect) generally only references a single B channel. In most cases you don't need to alter this setting.

Refer here for more details (from the CCM help page) -

Timeslot Number - B-channel usage always indicates actual timeslot map format (such as 1-15 and 17-31 for E1).

Slotmap - B-channel usage always indicates a slot map format.

Use Number When 1B - Channel usage indicates a channel map for one B-channel but indicates a slot map if more than one B-channel exists.

Continuous Number - Configures a continuous range of slot numbers (1-30) as the E1 logical channel number instead of the noncontinuous actual timeslot number (1-15 and 17-31).