If the number of samples per symbol (sps) is 4, then you should upsample by 4. The input to the pulse shaping filter is 1 sample/symbol, and the output is 4 samples per symbol, so the upsampling rate is 4.
The span is the number of symbol periods in the filter's impulse response. Intuitively, this means that a particular symbol influences the pulse-shaped output for 8 symbol periods, or that the pulse-shaped signal at any moment in time contains a linear combination of 8 different symbols. The number of taps in the filter is span*sps+1, which is 33 in this case. The delay of the filter is span/2. For a fixed filter span in symbol periods, the number of taps in the filter goes up with the number of samples per symbol because the output sample rate increases. However, the span of the filter in symbol periods and the upsampling factor are two independent variables. Changing the span does not change the upsampling rate. Changing the number of samples per symbol in the pulse shaping filter is equivalent to changing the upsampling rate.