Wherever vcs accepts times or intervals the following syntax can be used, it is meant to be readable. By default, when just a number is given, it will be interpreted as seconds.
You can add h, m and s and combine them to set the time. You can think of this as a translation of the usual time format 00:00:00.
Explained in more detail, the format follows the pattern: XhYmZs (no spaces allowed) with Xh, Ym, Z and s being optional and meaning: Xh: X is the number of hours, followed by a literal h, hence e.g. 2h stands for 2 hours. Ym: Y is the number of minutes, followed by a literal m, hence e.g. 30m stands for 30 minutes. Zs: Z is the number of seconds, optionally followed by a literal s, hence e.g. both 30s and 30 stand for 30 seconds.
The syntax is very permisive, you don't have to write time in clock-correct form, i.e. 1h90m90s is accepted and the same as 2h31m30.
88m: 88 minutes1h3: 1 hour and 3 seconds3600: 1 hour, same as 1h, 60m or 30m1800