how to find out what is the functionality of a procedure?

Hi all.

I encounter a problem knowing how a measure is calculated.

The roul group indicates the following:

sr0_rcppln <-dstkToStr( IpTtlPlnRcpO)

now i know how the measure IpTtlPlnRcpO is calculated but i don´t know how the procedure dstkToStr affects the measure to populate the sr0_rcppln measure.

also i have this expression of a rule and i don't know how to read it and what the WrpItemAlerts does :

Exp: IpSlsCrdDtdV, IpSCMDStkAltV, IpSCMDStlAltV, IpSCStkAltV, IpSCStlAltV, IpDmdCrdDtdV, IpDcStkAltV, IpDcMdStkAltV, IpOvrStkAltW, IpStlSurAltLV, IpSlsCrdAltW, IpDmdCrdAltW, IpOvrSkDtdAltV, IpSlSurMDAltV <- WrpItemAlerts(dmn_plnhzn, IpBydPlnHznG, IpLtI, IpMinLtI, dmn_rltsts, sr0_pckdmd, dmx_pszmap, sr0_pckco, IpBoSkuI, IpFxdPrdV, IpPscV, dm1_rectrg, dm1_stlinddef, dm1_stlindexc, dm1_mstcsmflg, IpScdStkG, IpScdStkD, IpScdStkE, IpScdSlG, IpScdSlD, IpScdSlE, IpScuStkG, IpScuStkD, IpScuStkE, IpScpsStkG, IpScpsStkD, IpScpsStkE, IpScuSlG, IpScuSlD, IpScuSlE, IpScpsSlG, IpScpsSlD, IpScpsSlE, IpDcuStkG, IpDcuStkD, IpDcuStkE, IpDcpStkG, IpDcpStkD, IpDcpStkE, IpDcdStkG, IpDcdStkD, IpDcdStkE, IpPrjInvSkuV, IpTtlPlnRcpSkuO, IpExpRcpSkuV, IpPSCDThrG, IpPSCDThrD, IpPSCDThrE, IpOvrStkThrG, IpOvrStkThrD, IpOvrStkThrE, IpSlsCrdDMI, IpDmdCrdDMI, IpOvrStkDMI, IpOrDmdO.level([prod].[sku]), IpDmdO.level([prod].[sku]), IpSlSurDayG, IpSlSurDayD, IpSlSurDayE, IpSlSurThrG, IpSlSurThrD, IpSlSurThrE, IpSlsCrdMskI, IpDmdCrdMskI, IpOvrStkMskI, IpSlSurMDThrG, IpSlSurMDThrD, IpSlSurMDThrE, IpRtV, IpActCmdI, IpHldBckQtyI, IpHldBckOptG, IpHldBckOptD, IpHldBckOptE, sr0_frh_g, sr0_frh_s, sr0_frh_i,  sr0_msqind_g, sr0_msqind_d, sr0_msqind_i, sr0_msqind_e, sr0_esind, IpRplMtdG, IpRplMtdD,