In order to send SMS messages using the Rules Engine, you need SMS credits. You can buy prepaid bundles of SMS credits. If you send an SMS message, the credit will decrease accordingly.
When you send an SMS message over 160 characters, the message will be split and result in multiple messages. You can choose if you want to truncate the message to 160 characters to make sure only at max one credit is deducted per message from your balance or if you always want to receive the full message which can result in multiple message credits being deducted.
The SMS standard says that large messages are segmented into 153 character segments and sent individually then rebuilt on the recipients device. This means that a 161 character message would result in two segments being deducted.
If you include non-GSM characters in your message, those messages have to be sent using the so-called UCS-2 encoding. Messages containing any non-GSM-character are limited to 70 characters. See a list of all GSM characters here: https://en.wikipedia.org/wiki/GSM_03.38#GSM_7-bit_default_alphabet_and_extension_table_of_3GPP_TS_23.038_.2F_GSM_03.38
In order to set up the truncation mode simply navigate into the billing section of your Datacake Workspace using the Side Bar.
In here you find the settings for truncation mode as shown on the above screenshot.
You can see a list of the last up to 100 SMS messages including their segment count in the billing administration.